Hello,
syzbot found the following issue on:
HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386
Unfortunately, I don't have any reproducer for this issue yet.
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
==================================================================
BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
can_madv_lru_vma mm/internal.h:76 [inline]
__oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
__do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
__do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf6e70549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Allocated by task 12778:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:436 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
kasan_slab_alloc include/linux/kasan.h:260 [inline]
slab_post_alloc_hook mm/slab.h:732 [inline]
slab_alloc_node mm/slub.c:3230 [inline]
slab_alloc mm/slub.c:3238 [inline]
kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
vm_area_dup+0x88/0x2b0 kernel/fork.c:357
dup_mmap kernel/fork.c:554 [inline]
dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
copy_mm kernel/fork.c:1503 [inline]
copy_process+0x71f8/0x7300 kernel/fork.c:2164
kernel_clone+0xe7/0xab0 kernel/fork.c:2555
__do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
__do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
Freed by task 12780:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:45
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
kasan_slab_free include/linux/kasan.h:236 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
slab_free mm/slub.c:3509 [inline]
kmem_cache_free+0xd8/0x340 mm/slub.c:3526
remove_vma+0x135/0x170 mm/mmap.c:189
exit_mmap+0x29a/0x670 mm/mmap.c:3186
__mmput+0x122/0x4b0 kernel/fork.c:1114
mmput+0x56/0x60 kernel/fork.c:1135
exit_mm kernel/exit.c:507 [inline]
do_exit+0xa3c/0x2a30 kernel/exit.c:793
do_group_exit+0xd2/0x2f0 kernel/exit.c:935
get_signal+0x4b0/0x28c0 kernel/signal.c:2862
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
__do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
The buggy address belongs to the object at ffff88807b868b58
which belongs to the cache vm_area_struct of size 200
The buggy address is located 80 bytes inside of
200-byte region [ffff88807b868b58, ffff88807b868c20)
The buggy address belongs to the page:
page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
memcg:ffff88804fe94a01
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
prep_new_page mm/page_alloc.c:2434 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
alloc_slab_page mm/slub.c:1799 [inline]
allocate_slab mm/slub.c:1944 [inline]
new_slab+0x28a/0x3b0 mm/slub.c:2004
___slab_alloc+0x87c/0xe90 mm/slub.c:3018
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
slab_alloc_node mm/slub.c:3196 [inline]
slab_alloc mm/slub.c:3238 [inline]
kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
vm_area_dup+0x88/0x2b0 kernel/fork.c:357
dup_mmap kernel/fork.c:554 [inline]
dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
copy_mm kernel/fork.c:1503 [inline]
copy_process+0x71f8/0x7300 kernel/fork.c:2164
kernel_clone+0xe7/0xab0 kernel/fork.c:2555
__do_sys_clone+0xc8/0x110 kernel/fork.c:2672
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1352 [inline]
free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
free_unref_page_prepare mm/page_alloc.c:3325 [inline]
free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
release_pages+0x317/0x1220 mm/swap.c:980
tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
tlb_flush_mmu mm/mmu_gather.c:250 [inline]
tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
exit_mmap+0x21b/0x670 mm/mmap.c:3180
__mmput+0x122/0x4b0 kernel/fork.c:1114
mmput+0x56/0x60 kernel/fork.c:1135
exit_mm kernel/exit.c:507 [inline]
do_exit+0xa3c/0x2a30 kernel/exit.c:793
do_group_exit+0xd2/0x2f0 kernel/exit.c:935
get_signal+0x4b0/0x28c0 kernel/signal.c:2862
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
__do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
Memory state around the buggy address:
ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
>ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
a: 10 06 adc %al,(%rsi)
c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
10: 10 07 adc %al,(%rdi)
12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
16: 10 08 adc %cl,(%rax)
18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1c: 00 00 add %al,(%rax)
1e: 00 00 add %al,(%rax)
20: 00 51 52 add %dl,0x52(%rcx)
23: 55 push %rbp
24: 89 e5 mov %esp,%ebp
26: 0f 34 sysenter
28: cd 80 int $0x80
* 2a: 5d pop %rbp <-- trapping instruction
2b: 5a pop %rdx
2c: 59 pop %rcx
2d: c3 retq
2e: 90 nop
2f: 90 nop
30: 90 nop
31: 90 nop
32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
---
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On Mon, Feb 14, 2022 at 2:44 AM syzbot
<[email protected]> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> ==================================================================
> BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
> BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
>
> CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
> __kasan_report mm/kasan/report.c:442 [inline]
> kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> can_madv_lru_vma mm/internal.h:76 [inline]
> __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> __do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
> do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> RIP: 0023:0xf6e70549
> Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
>
> Allocated by task 12778:
> kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> kasan_set_track mm/kasan/common.c:45 [inline]
> set_alloc_info mm/kasan/common.c:436 [inline]
> __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
> kasan_slab_alloc include/linux/kasan.h:260 [inline]
> slab_post_alloc_hook mm/slab.h:732 [inline]
> slab_alloc_node mm/slub.c:3230 [inline]
> slab_alloc mm/slub.c:3238 [inline]
> kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
> vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> dup_mmap kernel/fork.c:554 [inline]
> dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> copy_mm kernel/fork.c:1503 [inline]
> copy_process+0x71f8/0x7300 kernel/fork.c:2164
> kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> __do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
> do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
> Freed by task 12780:
> kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> kasan_set_track+0x21/0x30 mm/kasan/common.c:45
> kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
> ____kasan_slab_free mm/kasan/common.c:366 [inline]
> ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
> kasan_slab_free include/linux/kasan.h:236 [inline]
> slab_free_hook mm/slub.c:1728 [inline]
> slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
> slab_free mm/slub.c:3509 [inline]
> kmem_cache_free+0xd8/0x340 mm/slub.c:3526
> remove_vma+0x135/0x170 mm/mmap.c:189
> exit_mmap+0x29a/0x670 mm/mmap.c:3186
> __mmput+0x122/0x4b0 kernel/fork.c:1114
> mmput+0x56/0x60 kernel/fork.c:1135
> exit_mm kernel/exit.c:507 [inline]
> do_exit+0xa3c/0x2a30 kernel/exit.c:793
> do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> handle_signal_work kernel/entry/common.c:148 [inline]
> exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
It seems process_mrelease() may be racy with exiting. mmgrab() just
pin mm struct, but doesn't guarantee the associated address space
still exists. mmget or mmget_not_zero() may be needed at first glance.
The below untested patch (compiled) may be able to fix it.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 832fb330376e..c389995bcc71 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -1185,9 +1185,11 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
unsigned int, flags)
if (!reap)
goto drop_mm;
+ if (!mmget_not_zero(mm))
+ goto drop_mm;
if (mmap_read_lock_killable(mm)) {
ret = -EINTR;
- goto drop_mm;
+ goto put_mm;
}
/*
* Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
@@ -1197,6 +1199,8 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
unsigned int, flags)
ret = -EAGAIN;
mmap_read_unlock(mm);
+put_mm:
+ mmput(mm);
drop_mm:
mmdrop(mm);
put_task:
>
> The buggy address belongs to the object at ffff88807b868b58
> which belongs to the cache vm_area_struct of size 200
> The buggy address is located 80 bytes inside of
> 200-byte region [ffff88807b868b58, ffff88807b868c20)
> The buggy address belongs to the page:
> page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
> memcg:ffff88804fe94a01
> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
> raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
> prep_new_page mm/page_alloc.c:2434 [inline]
> get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
> __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
> alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
> alloc_slab_page mm/slub.c:1799 [inline]
> allocate_slab mm/slub.c:1944 [inline]
> new_slab+0x28a/0x3b0 mm/slub.c:2004
> ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
> __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
> slab_alloc_node mm/slub.c:3196 [inline]
> slab_alloc mm/slub.c:3238 [inline]
> kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
> vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> dup_mmap kernel/fork.c:554 [inline]
> dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> copy_mm kernel/fork.c:1503 [inline]
> copy_process+0x71f8/0x7300 kernel/fork.c:2164
> kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> __do_sys_clone+0xc8/0x110 kernel/fork.c:2672
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> page last free stack trace:
> reset_page_owner include/linux/page_owner.h:24 [inline]
> free_pages_prepare mm/page_alloc.c:1352 [inline]
> free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
> free_unref_page_prepare mm/page_alloc.c:3325 [inline]
> free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
> release_pages+0x317/0x1220 mm/swap.c:980
> tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
> tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
> tlb_flush_mmu mm/mmu_gather.c:250 [inline]
> tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
> exit_mmap+0x21b/0x670 mm/mmap.c:3180
> __mmput+0x122/0x4b0 kernel/fork.c:1114
> mmput+0x56/0x60 kernel/fork.c:1135
> exit_mm kernel/exit.c:507 [inline]
> do_exit+0xa3c/0x2a30 kernel/exit.c:793
> do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> handle_signal_work kernel/entry/common.c:148 [inline]
> exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
> Memory state around the buggy address:
> ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
> >ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
> ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> ----------------
> Code disassembly (best guess):
> 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
> 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
> a: 10 06 adc %al,(%rsi)
> c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> 10: 10 07 adc %al,(%rdi)
> 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> 16: 10 08 adc %cl,(%rax)
> 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> 1c: 00 00 add %al,(%rax)
> 1e: 00 00 add %al,(%rax)
> 20: 00 51 52 add %dl,0x52(%rcx)
> 23: 55 push %rbp
> 24: 89 e5 mov %esp,%ebp
> 26: 0f 34 sysenter
> 28: cd 80 int $0x80
> * 2a: 5d pop %rbp <-- trapping instruction
> 2b: 5a pop %rdx
> 2c: 59 pop %rcx
> 2d: c3 retq
> 2e: 90 nop
> 2f: 90 nop
> 30: 90 nop
> 31: 90 nop
> 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
[Add Suren - and keeping the full message for reference. My comment in
inlined]
On Mon 14-02-22 11:07:05, Yang Shi wrote:
> On Mon, Feb 14, 2022 at 2:44 AM syzbot
> <[email protected]> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> > dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > userspace arch: i386
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: [email protected]
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
> > BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
> >
> > CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:88 [inline]
> > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> > print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
> > __kasan_report mm/kasan/report.c:442 [inline]
> > kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> > can_madv_lru_vma mm/internal.h:76 [inline]
> > __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > __do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
> > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > RIP: 0023:0xf6e70549
> > Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> > RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > </TASK>
> >
> > Allocated by task 12778:
> > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > kasan_set_track mm/kasan/common.c:45 [inline]
> > set_alloc_info mm/kasan/common.c:436 [inline]
> > __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
> > kasan_slab_alloc include/linux/kasan.h:260 [inline]
> > slab_post_alloc_hook mm/slab.h:732 [inline]
> > slab_alloc_node mm/slub.c:3230 [inline]
> > slab_alloc mm/slub.c:3238 [inline]
> > kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
> > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > dup_mmap kernel/fork.c:554 [inline]
> > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > copy_mm kernel/fork.c:1503 [inline]
> > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > __do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
> > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> >
> > Freed by task 12780:
> > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > kasan_set_track+0x21/0x30 mm/kasan/common.c:45
> > kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
> > ____kasan_slab_free mm/kasan/common.c:366 [inline]
> > ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
> > kasan_slab_free include/linux/kasan.h:236 [inline]
> > slab_free_hook mm/slub.c:1728 [inline]
> > slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
> > slab_free mm/slub.c:3509 [inline]
> > kmem_cache_free+0xd8/0x340 mm/slub.c:3526
> > remove_vma+0x135/0x170 mm/mmap.c:189
> > exit_mmap+0x29a/0x670 mm/mmap.c:3186
> > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > mmput+0x56/0x60 kernel/fork.c:1135
> > exit_mm kernel/exit.c:507 [inline]
> > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > handle_signal_work kernel/entry/common.c:148 [inline]
> > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>
> It seems process_mrelease() may be racy with exiting. mmgrab() just
> pin mm struct, but doesn't guarantee the associated address space
> still exists. mmget or mmget_not_zero() may be needed at first glance.
This is what process_mrelease used to do before ba535c1caf3e
("mm/oom_kill: allow process_mrelease to run under mmap_lock
protection"). It shouldn't be really necessary because of the
synchronization that happens on the exit_mmap level. There were some
patches in that area and I am not sure whether something is still
hanging in the Andrew's queue. Suren will surely know better.
> The below untested patch (compiled) may be able to fix it.
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 832fb330376e..c389995bcc71 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1185,9 +1185,11 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> unsigned int, flags)
> if (!reap)
> goto drop_mm;
>
> + if (!mmget_not_zero(mm))
> + goto drop_mm;
> if (mmap_read_lock_killable(mm)) {
> ret = -EINTR;
> - goto drop_mm;
> + goto put_mm;
> }
> /*
> * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
> @@ -1197,6 +1199,8 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> unsigned int, flags)
> ret = -EAGAIN;
> mmap_read_unlock(mm);
>
> +put_mm:
> + mmput(mm);
> drop_mm:
> mmdrop(mm);
> put_task:
>
> >
> > The buggy address belongs to the object at ffff88807b868b58
> > which belongs to the cache vm_area_struct of size 200
> > The buggy address is located 80 bytes inside of
> > 200-byte region [ffff88807b868b58, ffff88807b868c20)
> > The buggy address belongs to the page:
> > page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
> > memcg:ffff88804fe94a01
> > flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> > raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
> > raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
> > prep_new_page mm/page_alloc.c:2434 [inline]
> > get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
> > __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
> > alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
> > alloc_slab_page mm/slub.c:1799 [inline]
> > allocate_slab mm/slub.c:1944 [inline]
> > new_slab+0x28a/0x3b0 mm/slub.c:2004
> > ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
> > __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
> > slab_alloc_node mm/slub.c:3196 [inline]
> > slab_alloc mm/slub.c:3238 [inline]
> > kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
> > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > dup_mmap kernel/fork.c:554 [inline]
> > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > copy_mm kernel/fork.c:1503 [inline]
> > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > __do_sys_clone+0xc8/0x110 kernel/fork.c:2672
> > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > page last free stack trace:
> > reset_page_owner include/linux/page_owner.h:24 [inline]
> > free_pages_prepare mm/page_alloc.c:1352 [inline]
> > free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
> > free_unref_page_prepare mm/page_alloc.c:3325 [inline]
> > free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
> > release_pages+0x317/0x1220 mm/swap.c:980
> > tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
> > tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
> > tlb_flush_mmu mm/mmu_gather.c:250 [inline]
> > tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
> > exit_mmap+0x21b/0x670 mm/mmap.c:3180
> > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > mmput+0x56/0x60 kernel/fork.c:1135
> > exit_mm kernel/exit.c:507 [inline]
> > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > handle_signal_work kernel/entry/common.c:148 [inline]
> > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> >
> > Memory state around the buggy address:
> > ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
> > >ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ^
> > ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
> > ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ==================================================================
> > ----------------
> > Code disassembly (best guess):
> > 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
> > 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
> > a: 10 06 adc %al,(%rsi)
> > c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> > 10: 10 07 adc %al,(%rdi)
> > 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> > 16: 10 08 adc %cl,(%rax)
> > 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> > 1c: 00 00 add %al,(%rax)
> > 1e: 00 00 add %al,(%rax)
> > 20: 00 51 52 add %dl,0x52(%rcx)
> > 23: 55 push %rbp
> > 24: 89 e5 mov %esp,%ebp
> > 26: 0f 34 sysenter
> > 28: cd 80 int $0x80
> > * 2a: 5d pop %rbp <-- trapping instruction
> > 2b: 5a pop %rdx
> > 2c: 59 pop %rcx
> > 2d: c3 retq
> > 2e: 90 nop
> > 2f: 90 nop
> > 30: 90 nop
> > 31: 90 nop
> > 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at [email protected].
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
--
Michal Hocko
SUSE Labs
->
On Tue, Feb 15, 2022 at 1:59 AM Michal Hocko <[email protected]> wrote:
>
> [Add Suren - and keeping the full message for reference. My comment in
> inlined]
>
> On Mon 14-02-22 11:07:05, Yang Shi wrote:
> > On Mon, Feb 14, 2022 at 2:44 AM syzbot
> > <[email protected]> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > userspace arch: i386
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: [email protected]
> > >
> > > ==================================================================
> > > BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
> > > BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
> > >
> > > CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > Call Trace:
> > > <TASK>
> > > __dump_stack lib/dump_stack.c:88 [inline]
> > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> > > print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
> > > __kasan_report mm/kasan/report.c:442 [inline]
> > > kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> > > can_madv_lru_vma mm/internal.h:76 [inline]
> > > __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > __do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
> > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > RIP: 0023:0xf6e70549
> > > Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> > > RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
> > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
> > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > > </TASK>
> > >
> > > Allocated by task 12778:
> > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > kasan_set_track mm/kasan/common.c:45 [inline]
> > > set_alloc_info mm/kasan/common.c:436 [inline]
> > > __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
> > > kasan_slab_alloc include/linux/kasan.h:260 [inline]
> > > slab_post_alloc_hook mm/slab.h:732 [inline]
> > > slab_alloc_node mm/slub.c:3230 [inline]
> > > slab_alloc mm/slub.c:3238 [inline]
> > > kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
> > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > dup_mmap kernel/fork.c:554 [inline]
> > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > copy_mm kernel/fork.c:1503 [inline]
> > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > __do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
> > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > >
> > > Freed by task 12780:
> > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > kasan_set_track+0x21/0x30 mm/kasan/common.c:45
> > > kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
> > > ____kasan_slab_free mm/kasan/common.c:366 [inline]
> > > ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
> > > kasan_slab_free include/linux/kasan.h:236 [inline]
> > > slab_free_hook mm/slub.c:1728 [inline]
> > > slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
> > > slab_free mm/slub.c:3509 [inline]
> > > kmem_cache_free+0xd8/0x340 mm/slub.c:3526
> > > remove_vma+0x135/0x170 mm/mmap.c:189
> > > exit_mmap+0x29a/0x670 mm/mmap.c:3186
> > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > mmput+0x56/0x60 kernel/fork.c:1135
> > > exit_mm kernel/exit.c:507 [inline]
> > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> >
> > It seems process_mrelease() may be racy with exiting. mmgrab() just
> > pin mm struct, but doesn't guarantee the associated address space
> > still exists. mmget or mmget_not_zero() may be needed at first glance.
>
> This is what process_mrelease used to do before ba535c1caf3e
> ("mm/oom_kill: allow process_mrelease to run under mmap_lock
> protection"). It shouldn't be really necessary because of the
> synchronization that happens on the exit_mmap level. There were some
> patches in that area and I am not sure whether something is still
> hanging in the Andrew's queue. Suren will surely know better.
Correct, the proposed change is what we were doing before 64591e8605d6
("mm: protect free_pgtables with mmap_lock write lock in exit_mmap")
and ba535c1caf3e ("mm/oom_kill: allow process_mrelease to run under
mmap_lock protection"). The first patch changed exit_mmap to call
unlock_range, free_pgtables and remove_vma under mmap_write_lock and
the second patch calls __oom_reap_task_mm under mmap_read_lock. From
the call stack IIUC __oom_reap_task_mm at
https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/oom_kill.c#L1196
is racing with remove_vma at
https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/mmap.c#L3186. The
mmap_lock should prevent this race and I don't see anything missing in
Andrew's tree. I'll go over the code again and re-check but so far I
don't see how this race could occur.
>
> > The below untested patch (compiled) may be able to fix it.
> >
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index 832fb330376e..c389995bcc71 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -1185,9 +1185,11 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > unsigned int, flags)
> > if (!reap)
> > goto drop_mm;
> >
> > + if (!mmget_not_zero(mm))
> > + goto drop_mm;
> > if (mmap_read_lock_killable(mm)) {
> > ret = -EINTR;
> > - goto drop_mm;
> > + goto put_mm;
> > }
> > /*
> > * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
> > @@ -1197,6 +1199,8 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > unsigned int, flags)
> > ret = -EAGAIN;
> > mmap_read_unlock(mm);
> >
> > +put_mm:
> > + mmput(mm);
> > drop_mm:
> > mmdrop(mm);
> > put_task:
> >
> > >
> > > The buggy address belongs to the object at ffff88807b868b58
> > > which belongs to the cache vm_area_struct of size 200
> > > The buggy address is located 80 bytes inside of
> > > 200-byte region [ffff88807b868b58, ffff88807b868c20)
> > > The buggy address belongs to the page:
> > > page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
> > > memcg:ffff88804fe94a01
> > > flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> > > raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
> > > raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
> > > page dumped because: kasan: bad access detected
> > > page_owner tracks the page as allocated
> > > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
> > > prep_new_page mm/page_alloc.c:2434 [inline]
> > > get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
> > > __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
> > > alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
> > > alloc_slab_page mm/slub.c:1799 [inline]
> > > allocate_slab mm/slub.c:1944 [inline]
> > > new_slab+0x28a/0x3b0 mm/slub.c:2004
> > > ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
> > > __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
> > > slab_alloc_node mm/slub.c:3196 [inline]
> > > slab_alloc mm/slub.c:3238 [inline]
> > > kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
> > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > dup_mmap kernel/fork.c:554 [inline]
> > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > copy_mm kernel/fork.c:1503 [inline]
> > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > __do_sys_clone+0xc8/0x110 kernel/fork.c:2672
> > > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > page last free stack trace:
> > > reset_page_owner include/linux/page_owner.h:24 [inline]
> > > free_pages_prepare mm/page_alloc.c:1352 [inline]
> > > free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
> > > free_unref_page_prepare mm/page_alloc.c:3325 [inline]
> > > free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
> > > release_pages+0x317/0x1220 mm/swap.c:980
> > > tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
> > > tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
> > > tlb_flush_mmu mm/mmu_gather.c:250 [inline]
> > > tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
> > > exit_mmap+0x21b/0x670 mm/mmap.c:3180
> > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > mmput+0x56/0x60 kernel/fork.c:1135
> > > exit_mm kernel/exit.c:507 [inline]
> > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > >
> > > Memory state around the buggy address:
> > > ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
> > > >ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ^
> > > ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
> > > ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ==================================================================
> > > ----------------
> > > Code disassembly (best guess):
> > > 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
> > > 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
> > > a: 10 06 adc %al,(%rsi)
> > > c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> > > 10: 10 07 adc %al,(%rdi)
> > > 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> > > 16: 10 08 adc %cl,(%rax)
> > > 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> > > 1c: 00 00 add %al,(%rax)
> > > 1e: 00 00 add %al,(%rax)
> > > 20: 00 51 52 add %dl,0x52(%rcx)
> > > 23: 55 push %rbp
> > > 24: 89 e5 mov %esp,%ebp
> > > 26: 0f 34 sysenter
> > > 28: cd 80 int $0x80
> > > * 2a: 5d pop %rbp <-- trapping instruction
> > > 2b: 5a pop %rdx
> > > 2c: 59 pop %rcx
> > > 2d: c3 retq
> > > 2e: 90 nop
> > > 2f: 90 nop
> > > 30: 90 nop
> > > 31: 90 nop
> > > 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > > 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > >
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at [email protected].
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > >
>
> --
> Michal Hocko
> SUSE Labs
On Tue, Feb 15, 2022 at 9:34 AM Suren Baghdasaryan <[email protected]> wrote:
>
> ->
> On Tue, Feb 15, 2022 at 1:59 AM Michal Hocko <[email protected]> wrote:
> >
> > [Add Suren - and keeping the full message for reference. My comment in
> > inlined]
> >
> > On Mon 14-02-22 11:07:05, Yang Shi wrote:
> > > On Mon, Feb 14, 2022 at 2:44 AM syzbot
> > > <[email protected]> wrote:
> > > >
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> > > > git tree: upstream
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
> > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > userspace arch: i386
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by: [email protected]
> > > >
> > > > ==================================================================
> > > > BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
> > > > BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > > Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
> > > >
> > > > CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > > Call Trace:
> > > > <TASK>
> > > > __dump_stack lib/dump_stack.c:88 [inline]
> > > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> > > > print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
> > > > __kasan_report mm/kasan/report.c:442 [inline]
> > > > kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> > > > can_madv_lru_vma mm/internal.h:76 [inline]
> > > > __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > > __do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
> > > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > > RIP: 0023:0xf6e70549
> > > > Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> > > > RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
> > > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
> > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > > > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> > > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > > > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > > > </TASK>
> > > >
> > > > Allocated by task 12778:
> > > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > > kasan_set_track mm/kasan/common.c:45 [inline]
> > > > set_alloc_info mm/kasan/common.c:436 [inline]
> > > > __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
> > > > kasan_slab_alloc include/linux/kasan.h:260 [inline]
> > > > slab_post_alloc_hook mm/slab.h:732 [inline]
> > > > slab_alloc_node mm/slub.c:3230 [inline]
> > > > slab_alloc mm/slub.c:3238 [inline]
> > > > kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
> > > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > > dup_mmap kernel/fork.c:554 [inline]
> > > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > > copy_mm kernel/fork.c:1503 [inline]
> > > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > > __do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
> > > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > >
> > > > Freed by task 12780:
> > > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > > kasan_set_track+0x21/0x30 mm/kasan/common.c:45
> > > > kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
> > > > ____kasan_slab_free mm/kasan/common.c:366 [inline]
> > > > ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
> > > > kasan_slab_free include/linux/kasan.h:236 [inline]
> > > > slab_free_hook mm/slub.c:1728 [inline]
> > > > slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
> > > > slab_free mm/slub.c:3509 [inline]
> > > > kmem_cache_free+0xd8/0x340 mm/slub.c:3526
> > > > remove_vma+0x135/0x170 mm/mmap.c:189
> > > > exit_mmap+0x29a/0x670 mm/mmap.c:3186
> > > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > > mmput+0x56/0x60 kernel/fork.c:1135
> > > > exit_mm kernel/exit.c:507 [inline]
> > > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > >
> > > It seems process_mrelease() may be racy with exiting. mmgrab() just
> > > pin mm struct, but doesn't guarantee the associated address space
> > > still exists. mmget or mmget_not_zero() may be needed at first glance.
> >
> > This is what process_mrelease used to do before ba535c1caf3e
> > ("mm/oom_kill: allow process_mrelease to run under mmap_lock
> > protection"). It shouldn't be really necessary because of the
> > synchronization that happens on the exit_mmap level. There were some
> > patches in that area and I am not sure whether something is still
> > hanging in the Andrew's queue. Suren will surely know better.
>
> Correct, the proposed change is what we were doing before 64591e8605d6
> ("mm: protect free_pgtables with mmap_lock write lock in exit_mmap")
> and ba535c1caf3e ("mm/oom_kill: allow process_mrelease to run under
> mmap_lock protection"). The first patch changed exit_mmap to call
> unlock_range, free_pgtables and remove_vma under mmap_write_lock and
> the second patch calls __oom_reap_task_mm under mmap_read_lock. From
> the call stack IIUC __oom_reap_task_mm at
> https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/oom_kill.c#L1196
> is racing with remove_vma at
> https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/mmap.c#L3186. The
> mmap_lock should prevent this race and I don't see anything missing in
> Andrew's tree. I'll go over the code again and re-check but so far I
> don't see how this race could occur.
Isn't the below race possible?
CPU A CPU B
exiting:
mmap_write_lock
remove_vma()
mmap_write_unlock
process_mrelease:
mmap_read_lock
__oom_reap_task_mm
mmap_read_unlock
>
> >
> > > The below untested patch (compiled) may be able to fix it.
> > >
> > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > index 832fb330376e..c389995bcc71 100644
> > > --- a/mm/oom_kill.c
> > > +++ b/mm/oom_kill.c
> > > @@ -1185,9 +1185,11 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > > unsigned int, flags)
> > > if (!reap)
> > > goto drop_mm;
> > >
> > > + if (!mmget_not_zero(mm))
> > > + goto drop_mm;
> > > if (mmap_read_lock_killable(mm)) {
> > > ret = -EINTR;
> > > - goto drop_mm;
> > > + goto put_mm;
> > > }
> > > /*
> > > * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
> > > @@ -1197,6 +1199,8 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > > unsigned int, flags)
> > > ret = -EAGAIN;
> > > mmap_read_unlock(mm);
> > >
> > > +put_mm:
> > > + mmput(mm);
> > > drop_mm:
> > > mmdrop(mm);
> > > put_task:
> > >
> > > >
> > > > The buggy address belongs to the object at ffff88807b868b58
> > > > which belongs to the cache vm_area_struct of size 200
> > > > The buggy address is located 80 bytes inside of
> > > > 200-byte region [ffff88807b868b58, ffff88807b868c20)
> > > > The buggy address belongs to the page:
> > > > page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
> > > > memcg:ffff88804fe94a01
> > > > flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> > > > raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
> > > > raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
> > > > page dumped because: kasan: bad access detected
> > > > page_owner tracks the page as allocated
> > > > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
> > > > prep_new_page mm/page_alloc.c:2434 [inline]
> > > > get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
> > > > __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
> > > > alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
> > > > alloc_slab_page mm/slub.c:1799 [inline]
> > > > allocate_slab mm/slub.c:1944 [inline]
> > > > new_slab+0x28a/0x3b0 mm/slub.c:2004
> > > > ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
> > > > __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
> > > > slab_alloc_node mm/slub.c:3196 [inline]
> > > > slab_alloc mm/slub.c:3238 [inline]
> > > > kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
> > > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > > dup_mmap kernel/fork.c:554 [inline]
> > > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > > copy_mm kernel/fork.c:1503 [inline]
> > > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > > __do_sys_clone+0xc8/0x110 kernel/fork.c:2672
> > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > > > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > > page last free stack trace:
> > > > reset_page_owner include/linux/page_owner.h:24 [inline]
> > > > free_pages_prepare mm/page_alloc.c:1352 [inline]
> > > > free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
> > > > free_unref_page_prepare mm/page_alloc.c:3325 [inline]
> > > > free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
> > > > release_pages+0x317/0x1220 mm/swap.c:980
> > > > tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
> > > > tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
> > > > tlb_flush_mmu mm/mmu_gather.c:250 [inline]
> > > > tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
> > > > exit_mmap+0x21b/0x670 mm/mmap.c:3180
> > > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > > mmput+0x56/0x60 kernel/fork.c:1135
> > > > exit_mm kernel/exit.c:507 [inline]
> > > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > >
> > > > Memory state around the buggy address:
> > > > ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
> > > > >ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > ^
> > > > ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
> > > > ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > ==================================================================
> > > > ----------------
> > > > Code disassembly (best guess):
> > > > 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
> > > > 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
> > > > a: 10 06 adc %al,(%rsi)
> > > > c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> > > > 10: 10 07 adc %al,(%rdi)
> > > > 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> > > > 16: 10 08 adc %cl,(%rax)
> > > > 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> > > > 1c: 00 00 add %al,(%rax)
> > > > 1e: 00 00 add %al,(%rax)
> > > > 20: 00 51 52 add %dl,0x52(%rcx)
> > > > 23: 55 push %rbp
> > > > 24: 89 e5 mov %esp,%ebp
> > > > 26: 0f 34 sysenter
> > > > 28: cd 80 int $0x80
> > > > * 2a: 5d pop %rbp <-- trapping instruction
> > > > 2b: 5a pop %rdx
> > > > 2c: 59 pop %rcx
> > > > 2d: c3 retq
> > > > 2e: 90 nop
> > > > 2f: 90 nop
> > > > 30: 90 nop
> > > > 31: 90 nop
> > > > 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > > > 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > > >
> > > >
> > > > ---
> > > > This report is generated by a bot. It may contain errors.
> > > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > > syzbot engineers can be reached at [email protected].
> > > >
> > > > syzbot will keep track of this issue. See:
> > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > > >
> >
> > --
> > Michal Hocko
> > SUSE Labs
On Tue, Feb 15, 2022 at 11:36 AM Michal Hocko <[email protected]> wrote:
>
> On Tue 15-02-22 10:10:53, Suren Baghdasaryan wrote:
> > On Tue, Feb 15, 2022 at 9:53 AM Yang Shi <[email protected]> wrote:
> [...]
> > > Isn't the below race possible?
> > >
> > > CPU A CPU B
> > > exiting:
> > > mmap_write_lock
> > > remove_vma()
> > > mmap_write_unlock
> > > process_mrelease:
> > > mmap_read_lock
> > > __oom_reap_task_mm
> > > mmap_read_unlock
> > >
> >
> > Sure, that sequence (would not call it a race) is possible but in this
> > case __oom_reap_task_mm will find no vmas in the mm because exit_mmap
> > freed and removed all of them.
>
> I didn't really have chance to have a closer look but I do not see
> exit_mmap doing mm->mmap = NULL so the pointer can be a freed vma unless
> I am missing something. I thought we've had it in your patches? Has this
> got lost somewhere in the process?
Doh! Yes, it looks like I completely missed the actual pointer. That
must be it since I don't see any other possibility. Will post a patch
shortly.
Thanks!
> --
> Michal Hocko
> SUSE Labs
On Tue, Feb 15, 2022 at 11:43 AM Suren Baghdasaryan <[email protected]> wrote:
>
> On Tue, Feb 15, 2022 at 11:36 AM Michal Hocko <[email protected]> wrote:
> >
> > On Tue 15-02-22 10:10:53, Suren Baghdasaryan wrote:
> > > On Tue, Feb 15, 2022 at 9:53 AM Yang Shi <[email protected]> wrote:
> > [...]
> > > > Isn't the below race possible?
> > > >
> > > > CPU A CPU B
> > > > exiting:
> > > > mmap_write_lock
> > > > remove_vma()
> > > > mmap_write_unlock
> > > > process_mrelease:
> > > > mmap_read_lock
> > > > __oom_reap_task_mm
> > > > mmap_read_unlock
> > > >
> > >
> > > Sure, that sequence (would not call it a race) is possible but in this
> > > case __oom_reap_task_mm will find no vmas in the mm because exit_mmap
> > > freed and removed all of them.
> >
> > I didn't really have chance to have a closer look but I do not see
> > exit_mmap doing mm->mmap = NULL so the pointer can be a freed vma unless
> > I am missing something. I thought we've had it in your patches? Has this
> > got lost somewhere in the process?
>
> Doh! Yes, it looks like I completely missed the actual pointer. That
> must be it since I don't see any other possibility. Will post a patch
> shortly.
Fix posted at https://lore.kernel.org/all/[email protected]/
> Thanks!
>
> > --
> > Michal Hocko
> > SUSE Labs
On Tue, Feb 15, 2022 at 9:53 AM Yang Shi <[email protected]> wrote:
>
> On Tue, Feb 15, 2022 at 9:34 AM Suren Baghdasaryan <[email protected]> wrote:
> >
> > ->
> > On Tue, Feb 15, 2022 at 1:59 AM Michal Hocko <[email protected]> wrote:
> > >
> > > [Add Suren - and keeping the full message for reference. My comment in
> > > inlined]
> > >
> > > On Mon 14-02-22 11:07:05, Yang Shi wrote:
> > > > On Mon, Feb 14, 2022 at 2:44 AM syzbot
> > > > <[email protected]> wrote:
> > > > >
> > > > > Hello,
> > > > >
> > > > > syzbot found the following issue on:
> > > > >
> > > > > HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> > > > > git tree: upstream
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1229b2f8700000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=2ccf63a4bd07cf39cab0
> > > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > > userspace arch: i386
> > > > >
> > > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > > >
> > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > Reported-by: [email protected]
> > > > >
> > > > > ==================================================================
> > > > > BUG: KASAN: use-after-free in can_madv_lru_vma mm/internal.h:76 [inline]
> > > > > BUG: KASAN: use-after-free in __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > > > Read of size 8 at addr ffff88807b868ba8 by task syz-executor.2/12778
> > > > >
> > > > > CPU: 0 PID: 12778 Comm: syz-executor.2 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > > > Call Trace:
> > > > > <TASK>
> > > > > __dump_stack lib/dump_stack.c:88 [inline]
> > > > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> > > > > print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
> > > > > __kasan_report mm/kasan/report.c:442 [inline]
> > > > > kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
> > > > > can_madv_lru_vma mm/internal.h:76 [inline]
> > > > > __oom_reap_task_mm+0x3a4/0x400 mm/oom_kill.c:529
> > > > > __do_sys_process_mrelease+0x3f2/0x450 mm/oom_kill.c:1196
> > > > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > > > RIP: 0023:0xf6e70549
> > > > > Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> > > > > RSP: 002b:00000000f586a5cc EFLAGS: 00000296 ORIG_RAX: 00000000000001c0
> > > > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
> > > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > > > > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> > > > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > > > > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > > > > </TASK>
> > > > >
> > > > > Allocated by task 12778:
> > > > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > > > kasan_set_track mm/kasan/common.c:45 [inline]
> > > > > set_alloc_info mm/kasan/common.c:436 [inline]
> > > > > __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
> > > > > kasan_slab_alloc include/linux/kasan.h:260 [inline]
> > > > > slab_post_alloc_hook mm/slab.h:732 [inline]
> > > > > slab_alloc_node mm/slub.c:3230 [inline]
> > > > > slab_alloc mm/slub.c:3238 [inline]
> > > > > kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3243
> > > > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > > > dup_mmap kernel/fork.c:554 [inline]
> > > > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > > > copy_mm kernel/fork.c:1503 [inline]
> > > > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > > > __do_compat_sys_ia32_clone+0xac/0xe0 arch/x86/kernel/sys_ia32.c:254
> > > > > do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> > > > > __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
> > > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > > >
> > > > > Freed by task 12780:
> > > > > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
> > > > > kasan_set_track+0x21/0x30 mm/kasan/common.c:45
> > > > > kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
> > > > > ____kasan_slab_free mm/kasan/common.c:366 [inline]
> > > > > ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
> > > > > kasan_slab_free include/linux/kasan.h:236 [inline]
> > > > > slab_free_hook mm/slub.c:1728 [inline]
> > > > > slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
> > > > > slab_free mm/slub.c:3509 [inline]
> > > > > kmem_cache_free+0xd8/0x340 mm/slub.c:3526
> > > > > remove_vma+0x135/0x170 mm/mmap.c:189
> > > > > exit_mmap+0x29a/0x670 mm/mmap.c:3186
> > > > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > > > mmput+0x56/0x60 kernel/fork.c:1135
> > > > > exit_mm kernel/exit.c:507 [inline]
> > > > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > >
> > > > It seems process_mrelease() may be racy with exiting. mmgrab() just
> > > > pin mm struct, but doesn't guarantee the associated address space
> > > > still exists. mmget or mmget_not_zero() may be needed at first glance.
> > >
> > > This is what process_mrelease used to do before ba535c1caf3e
> > > ("mm/oom_kill: allow process_mrelease to run under mmap_lock
> > > protection"). It shouldn't be really necessary because of the
> > > synchronization that happens on the exit_mmap level. There were some
> > > patches in that area and I am not sure whether something is still
> > > hanging in the Andrew's queue. Suren will surely know better.
> >
> > Correct, the proposed change is what we were doing before 64591e8605d6
> > ("mm: protect free_pgtables with mmap_lock write lock in exit_mmap")
> > and ba535c1caf3e ("mm/oom_kill: allow process_mrelease to run under
> > mmap_lock protection"). The first patch changed exit_mmap to call
> > unlock_range, free_pgtables and remove_vma under mmap_write_lock and
> > the second patch calls __oom_reap_task_mm under mmap_read_lock. From
> > the call stack IIUC __oom_reap_task_mm at
> > https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/oom_kill.c#L1196
> > is racing with remove_vma at
> > https://elixir.bootlin.com/linux/v5.17-rc4/source/mm/mmap.c#L3186. The
> > mmap_lock should prevent this race and I don't see anything missing in
> > Andrew's tree. I'll go over the code again and re-check but so far I
> > don't see how this race could occur.
>
> Isn't the below race possible?
>
> CPU A CPU B
> exiting:
> mmap_write_lock
> remove_vma()
> mmap_write_unlock
> process_mrelease:
> mmap_read_lock
> __oom_reap_task_mm
> mmap_read_unlock
>
Sure, that sequence (would not call it a race) is possible but in this
case __oom_reap_task_mm will find no vmas in the mm because exit_mmap
freed and removed all of them.
> >
> > >
> > > > The below untested patch (compiled) may be able to fix it.
> > > >
> > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > > index 832fb330376e..c389995bcc71 100644
> > > > --- a/mm/oom_kill.c
> > > > +++ b/mm/oom_kill.c
> > > > @@ -1185,9 +1185,11 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > > > unsigned int, flags)
> > > > if (!reap)
> > > > goto drop_mm;
> > > >
> > > > + if (!mmget_not_zero(mm))
> > > > + goto drop_mm;
> > > > if (mmap_read_lock_killable(mm)) {
> > > > ret = -EINTR;
> > > > - goto drop_mm;
> > > > + goto put_mm;
> > > > }
> > > > /*
> > > > * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
> > > > @@ -1197,6 +1199,8 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd,
> > > > unsigned int, flags)
> > > > ret = -EAGAIN;
> > > > mmap_read_unlock(mm);
> > > >
> > > > +put_mm:
> > > > + mmput(mm);
> > > > drop_mm:
> > > > mmdrop(mm);
> > > > put_task:
> > > >
> > > > >
> > > > > The buggy address belongs to the object at ffff88807b868b58
> > > > > which belongs to the cache vm_area_struct of size 200
> > > > > The buggy address is located 80 bytes inside of
> > > > > 200-byte region [ffff88807b868b58, ffff88807b868c20)
> > > > > The buggy address belongs to the page:
> > > > > page:ffffea0001ee1a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b868
> > > > > memcg:ffff88804fe94a01
> > > > > flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> > > > > raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888140006a00
> > > > > raw: 0000000000000000 00000000000f000f 00000001ffffffff ffff88804fe94a01
> > > > > page dumped because: kasan: bad access detected
> > > > > page_owner tracks the page as allocated
> > > > > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3175, ts 344170603641, free_ts 344164018467
> > > > > prep_new_page mm/page_alloc.c:2434 [inline]
> > > > > get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
> > > > > __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
> > > > > alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
> > > > > alloc_slab_page mm/slub.c:1799 [inline]
> > > > > allocate_slab mm/slub.c:1944 [inline]
> > > > > new_slab+0x28a/0x3b0 mm/slub.c:2004
> > > > > ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
> > > > > __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
> > > > > slab_alloc_node mm/slub.c:3196 [inline]
> > > > > slab_alloc mm/slub.c:3238 [inline]
> > > > > kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3243
> > > > > vm_area_dup+0x88/0x2b0 kernel/fork.c:357
> > > > > dup_mmap kernel/fork.c:554 [inline]
> > > > > dup_mm+0x5fa/0x13e0 kernel/fork.c:1451
> > > > > copy_mm kernel/fork.c:1503 [inline]
> > > > > copy_process+0x71f8/0x7300 kernel/fork.c:2164
> > > > > kernel_clone+0xe7/0xab0 kernel/fork.c:2555
> > > > > __do_sys_clone+0xc8/0x110 kernel/fork.c:2672
> > > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > > > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > > > > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > > > page last free stack trace:
> > > > > reset_page_owner include/linux/page_owner.h:24 [inline]
> > > > > free_pages_prepare mm/page_alloc.c:1352 [inline]
> > > > > free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
> > > > > free_unref_page_prepare mm/page_alloc.c:3325 [inline]
> > > > > free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
> > > > > release_pages+0x317/0x1220 mm/swap.c:980
> > > > > tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
> > > > > tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
> > > > > tlb_flush_mmu mm/mmu_gather.c:250 [inline]
> > > > > tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
> > > > > exit_mmap+0x21b/0x670 mm/mmap.c:3180
> > > > > __mmput+0x122/0x4b0 kernel/fork.c:1114
> > > > > mmput+0x56/0x60 kernel/fork.c:1135
> > > > > exit_mm kernel/exit.c:507 [inline]
> > > > > do_exit+0xa3c/0x2a30 kernel/exit.c:793
> > > > > do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> > > > > get_signal+0x4b0/0x28c0 kernel/signal.c:2862
> > > > > arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
> > > > > handle_signal_work kernel/entry/common.c:148 [inline]
> > > > > exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
> > > > > exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
> > > > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
> > > > > syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
> > > > > __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181
> > > > > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
> > > > > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > > > >
> > > > > Memory state around the buggy address:
> > > > > ffff88807b868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > > ffff88807b868b00: fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb
> > > > > >ffff88807b868b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > > ^
> > > > > ffff88807b868c00: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
> > > > > ffff88807b868c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > > ==================================================================
> > > > > ----------------
> > > > > Code disassembly (best guess):
> > > > > 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
> > > > > 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
> > > > > a: 10 06 adc %al,(%rsi)
> > > > > c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> > > > > 10: 10 07 adc %al,(%rdi)
> > > > > 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> > > > > 16: 10 08 adc %cl,(%rax)
> > > > > 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> > > > > 1c: 00 00 add %al,(%rax)
> > > > > 1e: 00 00 add %al,(%rax)
> > > > > 20: 00 51 52 add %dl,0x52(%rcx)
> > > > > 23: 55 push %rbp
> > > > > 24: 89 e5 mov %esp,%ebp
> > > > > 26: 0f 34 sysenter
> > > > > 28: cd 80 int $0x80
> > > > > * 2a: 5d pop %rbp <-- trapping instruction
> > > > > 2b: 5a pop %rdx
> > > > > 2c: 59 pop %rcx
> > > > > 2d: c3 retq
> > > > > 2e: 90 nop
> > > > > 2f: 90 nop
> > > > > 30: 90 nop
> > > > > 31: 90 nop
> > > > > 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > > > > 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> > > > >
> > > > >
> > > > > ---
> > > > > This report is generated by a bot. It may contain errors.
> > > > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > > > syzbot engineers can be reached at [email protected].
> > > > >
> > > > > syzbot will keep track of this issue. See:
> > > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > > > >
> > >
> > > --
> > > Michal Hocko
> > > SUSE Labs
On Tue 15-02-22 10:10:53, Suren Baghdasaryan wrote:
> On Tue, Feb 15, 2022 at 9:53 AM Yang Shi <[email protected]> wrote:
[...]
> > Isn't the below race possible?
> >
> > CPU A CPU B
> > exiting:
> > mmap_write_lock
> > remove_vma()
> > mmap_write_unlock
> > process_mrelease:
> > mmap_read_lock
> > __oom_reap_task_mm
> > mmap_read_unlock
> >
>
> Sure, that sequence (would not call it a race) is possible but in this
> case __oom_reap_task_mm will find no vmas in the mm because exit_mmap
> freed and removed all of them.
I didn't really have chance to have a closer look but I do not see
exit_mmap doing mm->mmap = NULL so the pointer can be a freed vma unless
I am missing something. I thought we've had it in your patches? Has this
got lost somewhere in the process?
--
Michal Hocko
SUSE Labs