Hello,
syzbot found the following crash on:
HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending
cookies. Check SNMP counters.
==================================================================
BUG: KASAN: use-after-free in rtnetlink_put_metrics+0x621/0x690
net/core/rtnetlink.c:754
Read of size 4 at addr ffff8801b3cd8b00 by task udevd/2613
CPU: 0 PID: 2613 Comm: udevd Not tainted 4.18.0-rc6+ #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
rtnetlink_put_metrics+0x621/0x690 net/core/rtnetlink.c:754
rt6_fill_node+0x7d9/0x1540 net/ipv6/route.c:4753
inet6_rt_notify+0x161/0x2c0 net/ipv6/route.c:4985
fib6_del_route net/ipv6/ip6_fib.c:1788 [inline]
fib6_del+0xf4d/0x1310 net/ipv6/ip6_fib.c:1815
fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
__fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
fib6_clean_all net/ipv6/ip6_fib.c:2051 [inline]
fib6_run_gc+0x182/0x3d0 net/ipv6/ip6_fib.c:2107
fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2124
call_timer_fn+0x242/0x970 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7a6/0xc70 kernel/time/timer.c:1666
run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
__do_softirq+0x2e8/0xb17 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x1d4/0x210 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:527 [inline]
smp_apic_timer_interrupt+0x186/0x730 arch/x86/kernel/apic/apic.c:1052
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783
[inline]
RIP: 0010:qlink_free mm/kasan/quarantine.c:150 [inline]
RIP: 0010:qlist_free_all+0xf8/0x160 mm/kasan/quarantine.c:166
Code: c7 40 10 00 00 00 00 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8
57 b8 a4 ff 48 83 3d 67 b4 37 06 00 74 56 48 89 df 57 9d <0f> 1f 44 00 00
eb af ba 00 00 00 80 48 01 c2 72 43 48 b9 00 00 00
RSP: 0018:ffff8801b54a7b08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000007 RBX: 0000000000000286 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8801b5498a38 RDI: 0000000000000286
RBP: ffff8801b54a7b40 R08: ffff8801b5498a38 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801dad85dc0 R14: ffff8801b37ace00 R15: ffffffff87f1b0a0
quarantine_reduce+0x163/0x1a0 mm/kasan/quarantine.c:259
kasan_kmalloc+0x99/0xe0 mm/kasan/kasan.c:538
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
slab_post_alloc_hook mm/slab.h:444 [inline]
slab_alloc mm/slab.c:3392 [inline]
kmem_cache_alloc+0x11b/0x760 mm/slab.c:3552
getname_flags+0xd0/0x5a0 fs/namei.c:140
user_path_at_empty+0x2d/0x50 fs/namei.c:2584
do_readlinkat+0x14b/0x400 fs/stat.c:394
__do_sys_readlink fs/stat.c:427 [inline]
__se_sys_readlink fs/stat.c:424 [inline]
__x64_sys_readlink+0x78/0xb0 fs/stat.c:424
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7efd8271b577
Code: f0 ff ff 77 02 f3 c3 48 8b 15 bd 38 2b 00 f7 d8 64 89 02 83 c8 ff c3
90 90 90 90 90 90 90 90 90 90 90 90 b8 59 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 73 01 c3 48 8b 0d 91 38 2b 00 31 d2 48 29 c2 64
RSP: 002b:00007ffe27d23688 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00000000021de250 RCX: 00007efd8271b577
RDX: 0000000000000400 RSI: 00007ffe27d23690 RDI: 00007ffe27d23b70
RBP: 00007ffe27d243b0 R08: 00007ffe27d243b0 R09: 00007efd8276fdc0
R10: 7665642f7379732f R11: 0000000000000246 R12: 00007ffe27d23b70
R13: 0000000000000400 R14: 00000000021de250 R15: 00000000021e3e10
Allocated by task 8953:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
fib6_metric_set+0x163/0x2c0 net/ipv6/ip6_fib.c:645
fib6_add_rt2node+0xe36/0x27f0 net/ipv6/ip6_fib.c:1000
fib6_add+0xaae/0x14d0 net/ipv6/ip6_fib.c:1308
__ip6_ins_rt+0x54/0x80 net/ipv6/route.c:1163
ip6_route_add+0x6d/0xc0 net/ipv6/route.c:3171
addrconf_prefix_route.isra.48+0x51d/0x720 net/ipv6/addrconf.c:2347
inet6_addr_modify net/ipv6/addrconf.c:4627 [inline]
inet6_rtm_newaddr+0x112e/0x1b50 net/ipv6/addrconf.c:4743
rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4665
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2453
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4683
netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline]
netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1341
netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1906
sock_sendmsg_nosec net/socket.c:642 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:652
___sys_sendmsg+0x7fd/0x930 net/socket.c:2126
__sys_sendmsg+0x11d/0x290 net/socket.c:2164
__do_sys_sendmsg net/socket.c:2173 [inline]
__se_sys_sendmsg net/socket.c:2171 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2171
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 2613:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xd9/0x260 mm/slab.c:3813
fib6_metrics_release+0x77/0x90 net/ipv6/ip6_fib.c:179
fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline]
fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934
fib6_del_route net/ipv6/ip6_fib.c:1784 [inline]
fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815
fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
__fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
fib6_clean_all net/ipv6/ip6_fib.c:2051 [inline]
fib6_run_gc+0x182/0x3d0 net/ipv6/ip6_fib.c:2107
fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2124
call_timer_fn+0x242/0x970 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7a6/0xc70 kernel/time/timer.c:1666
run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
__do_softirq+0x2e8/0xb17 kernel/softirq.c:292
The buggy address belongs to the object at ffff8801b3cd8b00
which belongs to the cache kmalloc-96 of size 96
The buggy address is located 0 bytes inside of
96-byte region [ffff8801b3cd8b00, ffff8801b3cd8b60)
The buggy address belongs to the page:
page:ffffea0006cf3600 count:1 mapcount:0 mapping:ffff8801dac004c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006a6f3c8 ffffea0007018608 ffff8801dac004c0
raw: 0000000000000000 ffff8801b3cd8000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8801b3cd8a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff8801b3cd8a80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8801b3cd8b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff8801b3cd8b80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff8801b3cd8c00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================
---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot.
On 07/31/2018 05:31 AM, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
> dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: [email protected]
>
> TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies. Check SNMP counters.
> ==================================================================
> BUG: KASAN: use-after-free in rtnetlink_put_metrics+0x621/0x690 net/core/rtnetlink.c:754
> Read of size 4 at addr ffff8801b3cd8b00 by task udevd/2613
>
> CPU: 0 PID: 2613 Comm: udevd Not tainted 4.18.0-rc6+ #34
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
> print_address_description+0x6c/0x20b mm/kasan/report.c:256
> kasan_report_error mm/kasan/report.c:354 [inline]
> kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
> __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
> rtnetlink_put_metrics+0x621/0x690 net/core/rtnetlink.c:754
> rt6_fill_node+0x7d9/0x1540 net/ipv6/route.c:4753
> inet6_rt_notify+0x161/0x2c0 net/ipv6/route.c:4985
> fib6_del_route net/ipv6/ip6_fib.c:1788 [inline]
> fib6_del+0xf4d/0x1310 net/ipv6/ip6_fib.c:1815
> fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
> fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
> fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
> fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
> __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
> fib6_clean_all net/ipv6/ip6_fib.c:2051 [inline]
> fib6_run_gc+0x182/0x3d0 net/ipv6/ip6_fib.c:2107
> fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2124
> call_timer_fn+0x242/0x970 kernel/time/timer.c:1326
> expire_timers kernel/time/timer.c:1363 [inline]
> __run_timers+0x7a6/0xc70 kernel/time/timer.c:1666
> run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
> __do_softirq+0x2e8/0xb17 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:372 [inline]
> irq_exit+0x1d4/0x210 kernel/softirq.c:412
> exiting_irq arch/x86/include/asm/apic.h:527 [inline]
> smp_apic_timer_interrupt+0x186/0x730 arch/x86/kernel/apic/apic.c:1052
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
> </IRQ>
> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783 [inline]
> RIP: 0010:qlink_free mm/kasan/quarantine.c:150 [inline]
> RIP: 0010:qlist_free_all+0xf8/0x160 mm/kasan/quarantine.c:166
> Code: c7 40 10 00 00 00 00 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 57 b8 a4 ff 48 83 3d 67 b4 37 06 00 74 56 48 89 df 57 9d <0f> 1f 44 00 00 eb af ba 00 00 00 80 48 01 c2 72 43 48 b9 00 00 00
> RSP: 0018:ffff8801b54a7b08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
> RAX: 0000000000000007 RBX: 0000000000000286 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff8801b5498a38 RDI: 0000000000000286
> RBP: ffff8801b54a7b40 R08: ffff8801b5498a38 R09: 0000000000000006
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: ffff8801dad85dc0 R14: ffff8801b37ace00 R15: ffffffff87f1b0a0
> quarantine_reduce+0x163/0x1a0 mm/kasan/quarantine.c:259
> kasan_kmalloc+0x99/0xe0 mm/kasan/kasan.c:538
> kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
> slab_post_alloc_hook mm/slab.h:444 [inline]
> slab_alloc mm/slab.c:3392 [inline]
> kmem_cache_alloc+0x11b/0x760 mm/slab.c:3552
> getname_flags+0xd0/0x5a0 fs/namei.c:140
> user_path_at_empty+0x2d/0x50 fs/namei.c:2584
> do_readlinkat+0x14b/0x400 fs/stat.c:394
> __do_sys_readlink fs/stat.c:427 [inline]
> __se_sys_readlink fs/stat.c:424 [inline]
> __x64_sys_readlink+0x78/0xb0 fs/stat.c:424
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7efd8271b577
> Code: f0 ff ff 77 02 f3 c3 48 8b 15 bd 38 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 90 90 90 90 90 90 90 90 90 b8 59 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 91 38 2b 00 31 d2 48 29 c2 64
> RSP: 002b:00007ffe27d23688 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
> RAX: ffffffffffffffda RBX: 00000000021de250 RCX: 00007efd8271b577
> RDX: 0000000000000400 RSI: 00007ffe27d23690 RDI: 00007ffe27d23b70
> RBP: 00007ffe27d243b0 R08: 00007ffe27d243b0 R09: 00007efd8276fdc0
> R10: 7665642f7379732f R11: 0000000000000246 R12: 00007ffe27d23b70
> R13: 0000000000000400 R14: 00000000021de250 R15: 00000000021e3e10
>
> Allocated by task 8953:
> save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> set_track mm/kasan/kasan.c:460 [inline]
> kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
> kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
> kmalloc include/linux/slab.h:513 [inline]
> kzalloc include/linux/slab.h:707 [inline]
> fib6_metric_set+0x163/0x2c0 net/ipv6/ip6_fib.c:645
> fib6_add_rt2node+0xe36/0x27f0 net/ipv6/ip6_fib.c:1000
> fib6_add+0xaae/0x14d0 net/ipv6/ip6_fib.c:1308
> __ip6_ins_rt+0x54/0x80 net/ipv6/route.c:1163
> ip6_route_add+0x6d/0xc0 net/ipv6/route.c:3171
> addrconf_prefix_route.isra.48+0x51d/0x720 net/ipv6/addrconf.c:2347
> inet6_addr_modify net/ipv6/addrconf.c:4627 [inline]
> inet6_rtm_newaddr+0x112e/0x1b50 net/ipv6/addrconf.c:4743
> rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4665
> netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2453
> rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4683
> netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline]
> netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1341
> netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1906
> sock_sendmsg_nosec net/socket.c:642 [inline]
> sock_sendmsg+0xd5/0x120 net/socket.c:652
> ___sys_sendmsg+0x7fd/0x930 net/socket.c:2126
> __sys_sendmsg+0x11d/0x290 net/socket.c:2164
> __do_sys_sendmsg net/socket.c:2173 [inline]
> __se_sys_sendmsg net/socket.c:2171 [inline]
> __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2171
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 2613:
> save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> set_track mm/kasan/kasan.c:460 [inline]
> __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
> kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
> __cache_free mm/slab.c:3498 [inline]
> kfree+0xd9/0x260 mm/slab.c:3813
> fib6_metrics_release+0x77/0x90 net/ipv6/ip6_fib.c:179
> fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline]
> fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934
> fib6_del_route net/ipv6/ip6_fib.c:1784 [inline]
> fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815
> fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
> fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
> fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
> fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
> __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
> fib6_clean_all net/ipv6/ip6_fib.c:2051 [inline]
> fib6_run_gc+0x182/0x3d0 net/ipv6/ip6_fib.c:2107
> fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2124
> call_timer_fn+0x242/0x970 kernel/time/timer.c:1326
> expire_timers kernel/time/timer.c:1363 [inline]
> __run_timers+0x7a6/0xc70 kernel/time/timer.c:1666
> run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
> __do_softirq+0x2e8/0xb17 kernel/softirq.c:292
>
> The buggy address belongs to the object at ffff8801b3cd8b00
> which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 0 bytes inside of
> 96-byte region [ffff8801b3cd8b00, ffff8801b3cd8b60)
> The buggy address belongs to the page:
> page:ffffea0006cf3600 count:1 mapcount:0 mapping:ffff8801dac004c0 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffffea0006a6f3c8 ffffea0007018608 ffff8801dac004c0
> raw: 0000000000000000 ffff8801b3cd8000 0000000100000020 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8801b3cd8a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8801b3cd8a80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>> ffff8801b3cd8b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ^
> ffff8801b3cd8b80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8801b3cd8c00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ==================================================================
>
>
> ---
> This bug 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 bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.
Probably also caused by :
commit df18b50448fab1dff093731dfd0e25e77e1afcd1
Author: Sabrina Dubroca <[email protected]>
Date: Mon Jul 30 16:23:10 2018 +0200
net/ipv6: fix metrics leak
2018-07-31, 05:41:56 -0700, Eric Dumazet wrote:
>
>
> On 07/31/2018 05:31 AM, syzbot wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
> > git tree: net
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
> > dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
> > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
[...]
> Probably also caused by :
>
>
> commit df18b50448fab1dff093731dfd0e25e77e1afcd1
> Author: Sabrina Dubroca <[email protected]>
> Date: Mon Jul 30 16:23:10 2018 +0200
>
> net/ipv6: fix metrics leak
Yeah, I'm looking into both those reports :/
--
Sabrina
From: Sabrina Dubroca <[email protected]>
Date: Tue, 31 Jul 2018 15:40:14 +0200
> 2018-07-31, 05:41:56 -0700, Eric Dumazet wrote:
>> Probably also caused by :
>>
>>
>> commit df18b50448fab1dff093731dfd0e25e77e1afcd1
>> Author: Sabrina Dubroca <[email protected]>
>> Date: Mon Jul 30 16:23:10 2018 +0200
>>
>> net/ipv6: fix metrics leak
>
> Yeah, I'm looking into both those reports :/
Please get me a fix for this soon, because as you can imagine this is
going to hold up the 4.18 release.
Thanks.
On Tue, Jul 31, 2018 at 6:41 AM Sabrina Dubroca <[email protected]> wrote:
>
> 2018-07-31, 05:41:56 -0700, Eric Dumazet wrote:
> >
> >
> > On 07/31/2018 05:31 AM, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
> > > git tree: net
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
> > > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> > >
> > > Unfortunately, I don't have any reproducer for this crash yet.
> [...]
>
> > Probably also caused by :
> >
> >
> > commit df18b50448fab1dff093731dfd0e25e77e1afcd1
> > Author: Sabrina Dubroca <[email protected]>
> > Date: Mon Jul 30 16:23:10 2018 +0200
> >
> > net/ipv6: fix metrics leak
>
> Yeah, I'm looking into both those reports :/
Looks like this commit is completely unnecessary,
fib6_drop_pcpu_from() calls fib6_info_release()
which calls fib6_info_destroy_rcu(), so this metrics
will be released twice...
2018-07-31, 16:03:13 -0700, Cong Wang wrote:
> On Tue, Jul 31, 2018 at 6:41 AM Sabrina Dubroca <[email protected]> wrote:
> >
> > 2018-07-31, 05:41:56 -0700, Eric Dumazet wrote:
> > >
> > >
> > > On 07/31/2018 05:31 AM, syzbot wrote:
> > > > Hello,
> > > >
> > > > syzbot found the following crash on:
> > > >
> > > > HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
> > > > git tree: net
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
> > > > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> > > >
> > > > Unfortunately, I don't have any reproducer for this crash yet.
> > [...]
> >
> > > Probably also caused by :
> > >
> > >
> > > commit df18b50448fab1dff093731dfd0e25e77e1afcd1
> > > Author: Sabrina Dubroca <[email protected]>
> > > Date: Mon Jul 30 16:23:10 2018 +0200
> > >
> > > net/ipv6: fix metrics leak
> >
> > Yeah, I'm looking into both those reports :/
>
> Looks like this commit is completely unnecessary,
> fib6_drop_pcpu_from() calls fib6_info_release()
> which calls fib6_info_destroy_rcu(), so this metrics
> will be released twice...
kmemleak disagrees:
unreferenced object 0xffff88006b605080 (size 96):
comm "ip", pid 433, jiffies 4294889793 (age 74.844s)
hex dump (first 32 bytes):
00 00 00 00 f4 01 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<000000002650e4e2>] ip6_route_info_create+0x770/0x4050
[<000000000a8d4c52>] ip6_route_add+0x18/0x90
[<00000000474d669c>] inet6_rtm_newroute+0xeb/0x100
[<0000000019fb732d>] rtnetlink_rcv_msg+0x3b5/0xb40
[<000000006f891e19>] netlink_rcv_skb+0x137/0x380
[<0000000070451985>] netlink_unicast+0x47f/0x6e0
[<000000004487d656>] netlink_sendmsg+0x7a7/0x10c0
[<0000000089fdf5ae>] sock_sendmsg+0xac/0x160
[<00000000aae19c54>] ___sys_sendmsg+0x6e0/0xbb0
[<00000000a3906352>] __sys_sendmsg+0xdc/0x230
[<00000000c7c8548a>] do_syscall_64+0x15d/0x740
[<000000007dfdad73>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[<000000003adb705a>] 0xffffffffffffffff
ip netns add peerA
ip link add eth0 netns peerA type veth peer name ethA
ip -net peerA link set eth0 up
ip -net peerA link set lo up
ip -net peerA a a fec0:A::1/64 dev eth0
ip -net peerA route add fec0:B::/64 via fec0:A:: mtu 1300
ip netns exec peerA nc fec0:B::1 1234
ip -net peerA route del fec0:B::/64
ip netns del peerA
--
Sabrina
On 8/1/18 10:15 AM, Sabrina Dubroca wrote:
> ip -net peerA route add fec0:B::/64 via fec0:A:: mtu 1300
I am on vacation right now with limited access to internet, so not able
to take a look.
In submitting the fib6_info changes I did tests like this and did not
see memleak reports (and verified the metrics refcnts with printks), so
I am surprised to see your patch in this area. Will take a look when I
can but that will not be for a couple more weeks.
From: Cong Wang <[email protected]>
Date: Tue, 31 Jul 2018 16:03:13 -0700
> Looks like this commit is completely unnecessary,
> fib6_drop_pcpu_from() calls fib6_info_release()
> which calls fib6_info_destroy_rcu(), so this metrics
> will be released twice...
And even if there was a leak here, it's illegal to free this
metrics memory synchronously since it is RCU protected.
That's why it normally goes through fib6_info_destroy_rcu().
Sabrina, I'm going to revert your changes unless I see some
progress here by the end of today.
2018-08-01, 11:46:36 -0700, David Miller wrote:
> From: Cong Wang <[email protected]>
> Date: Tue, 31 Jul 2018 16:03:13 -0700
>
> > Looks like this commit is completely unnecessary,
> > fib6_drop_pcpu_from() calls fib6_info_release()
> > which calls fib6_info_destroy_rcu(), so this metrics
> > will be released twice...
>
> And even if there was a leak here, it's illegal to free this
> metrics memory synchronously since it is RCU protected.
Yeah, I noticed that today, but I don't think that's the problem we're
seeing here.
> That's why it normally goes through fib6_info_destroy_rcu().
>
> Sabrina, I'm going to revert your changes unless I see some
> progress here by the end of today.
Yeah, I'm fine with a revert, we can fix the leak later.
syzbot hasn't found a reproducer so I'm not sure it's the same issue,
but I ran into this: we can create a route, start using it, and then
give it some metrics. In that case, we'll hit rt6_set_from() with the
default metrics, so we don't refcount them. Then fib6_metric_set()
will assign the new metrics to the parent route.
Then fib6_drop_pcpu_from will see that the parent route has
non-default metrics, and try to release this, but the percpu copy
doesn't actually hold a reference. Bandaid would be to put a
DST_METRICS_REFCOUNTED check in fib6_drop_pcpu_from().
Looking at rt6_set_from(), it seems we can also do dst_init_metrics
with the old metrics, then refcount the new metrics.
And I'm not sure whether the refcount_set in fib6_metric_set() can't
be reordered so that rt6_set_from() might see the new metrics pointer,
increment the refcount, then fib6_metric_set() would do its
refcount_set, stepping over the previous increment.
--
Sabrina
On Wed, Aug 1, 2018 at 1:15 AM Sabrina Dubroca <[email protected]> wrote:
>
> 2018-07-31, 16:03:13 -0700, Cong Wang wrote:
> > On Tue, Jul 31, 2018 at 6:41 AM Sabrina Dubroca <[email protected]> wrote:
> > >
> > > 2018-07-31, 05:41:56 -0700, Eric Dumazet wrote:
> > > >
> > > >
> > > > On 07/31/2018 05:31 AM, syzbot wrote:
> > > > > Hello,
> > > > >
> > > > > syzbot found the following crash on:
> > > > >
> > > > > HEAD commit: 61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups
> > > > > git tree: net
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=14a9de58400000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=41f9c04b50ef70c66947
> > > > > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> > > > >
> > > > > Unfortunately, I don't have any reproducer for this crash yet.
> > > [...]
> > >
> > > > Probably also caused by :
> > > >
> > > >
> > > > commit df18b50448fab1dff093731dfd0e25e77e1afcd1
> > > > Author: Sabrina Dubroca <[email protected]>
> > > > Date: Mon Jul 30 16:23:10 2018 +0200
> > > >
> > > > net/ipv6: fix metrics leak
> > >
> > > Yeah, I'm looking into both those reports :/
> >
> > Looks like this commit is completely unnecessary,
> > fib6_drop_pcpu_from() calls fib6_info_release()
> > which calls fib6_info_destroy_rcu(), so this metrics
> > will be released twice...
>
> kmemleak disagrees:
This information is missing from changelog. :)
>
> unreferenced object 0xffff88006b605080 (size 96):
> comm "ip", pid 433, jiffies 4294889793 (age 74.844s)
> hex dump (first 32 bytes):
> 00 00 00 00 f4 01 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<000000002650e4e2>] ip6_route_info_create+0x770/0x4050
> [<000000000a8d4c52>] ip6_route_add+0x18/0x90
> [<00000000474d669c>] inet6_rtm_newroute+0xeb/0x100
> [<0000000019fb732d>] rtnetlink_rcv_msg+0x3b5/0xb40
> [<000000006f891e19>] netlink_rcv_skb+0x137/0x380
> [<0000000070451985>] netlink_unicast+0x47f/0x6e0
> [<000000004487d656>] netlink_sendmsg+0x7a7/0x10c0
> [<0000000089fdf5ae>] sock_sendmsg+0xac/0x160
> [<00000000aae19c54>] ___sys_sendmsg+0x6e0/0xbb0
> [<00000000a3906352>] __sys_sendmsg+0xdc/0x230
> [<00000000c7c8548a>] do_syscall_64+0x15d/0x740
> [<000000007dfdad73>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [<000000003adb705a>] 0xffffffffffffffff
My kernel dev machine is broken now.
I will take a look tomorrow after I fix my kernel dev machine.
Thanks!