Hello,
I am hitting the following use-after-free reports while running
syzkaller fuzzer on commit c82be9d2244aacea9851c86f4fb74694c99cd874:
==================================================================
BUG: KASAN: use-after-free in ida_get_new_above+0x564/0x9b0
lib/idr.c:295 at addr ffff880160ef3600
Write of size 128 by task syz-executor1/1757
CPU: 1 PID: 1757 Comm: syz-executor1 Not tainted 4.10.0+ #98
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
kasan_object_err+0x1c/0x70 mm/kasan/report.c:162
print_address_description mm/kasan/report.c:200 [inline]
kasan_report_error mm/kasan/report.c:289 [inline]
kasan_report.part.2+0x1e5/0x4b0 mm/kasan/report.c:311
kasan_report+0x21/0x30 mm/kasan/report.c:298
check_memory_region_inline mm/kasan/kasan.c:315 [inline]
check_memory_region+0x139/0x190 mm/kasan/kasan.c:322
memset+0x23/0x40 mm/kasan/kasan.c:340
ida_get_new_above+0x564/0x9b0 lib/idr.c:295
ida_get_new include/linux/idr.h:209 [inline]
proc_alloc_inum+0x97/0x1f0 fs/proc/generic.c:201
proc_register+0x25/0x2f0 fs/proc/generic.c:338
proc_create_data+0x100/0x190 fs/proc/generic.c:509
proc_create include/linux/proc_fs.h:35 [inline]
ip_rt_do_proc_init+0x53/0x110 net/ipv4/route.c:382
ops_init+0x10a/0x530 net/core/net_namespace.c:115
setup_net+0x2ed/0x690 net/core/net_namespace.c:291
copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
SYSC_unshare kernel/fork.c:2281 [inline]
SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x44fb79
RSP: 002b:00007f1b66930b58 EFLAGS: 00000212 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044fb79
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062020200
RBP: 0000000062020200 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000007082a0
R13: 0000000000000004 R14: 0000000000000400 R15: 0000000000000000
Object at ffff880160ef3600, in cache kmalloc-128 size: 128
Allocated:
PID = 1730
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:502
set_track mm/kasan/kasan.c:514 [inline]
kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605
kmem_cache_alloc_trace+0x10b/0x670 mm/slab.c:3634
kmalloc include/linux/slab.h:490 [inline]
ida_pre_get+0xcd/0xe0 lib/radix-tree.c:2129
proc_alloc_inum+0xc5/0x1f0 fs/proc/generic.c:197
proc_register+0x25/0x2f0 fs/proc/generic.c:338
proc_create_data+0x100/0x190 fs/proc/generic.c:509
proc_create include/linux/proc_fs.h:35 [inline]
packet_net_init+0x8d/0xb0 net/packet/af_packet.c:4488
ops_init+0x10a/0x530 net/core/net_namespace.c:115
setup_net+0x2ed/0x690 net/core/net_namespace.c:291
copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
SYSC_unshare kernel/fork.c:2281 [inline]
SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 1648
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:502
set_track mm/kasan/kasan.c:514 [inline]
kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:578
__cache_free mm/slab.c:3510 [inline]
kfree+0xd3/0x250 mm/slab.c:3827
ida_pre_get+0x8a/0xe0 lib/radix-tree.c:2133
ida_simple_get+0x168/0x320 lib/idr.c:443
__kernfs_new_node+0xfe/0x3c0 fs/kernfs/dir.c:633
kernfs_new_node+0x80/0xe0 fs/kernfs/dir.c:661
kernfs_create_dir_ns+0x41/0x140 fs/kernfs/dir.c:933
kernfs_create_dir include/linux/kernfs.h:477 [inline]
internal_create_group+0xf7/0x8f0 fs/sysfs/group.c:124
sysfs_create_group fs/sysfs/group.c:156 [inline]
sysfs_create_groups+0x97/0x130 fs/sysfs/group.c:183
device_add_groups drivers/base/core.c:1031 [inline]
device_add_attrs drivers/base/core.c:1058 [inline]
device_add+0xb2f/0x1650 drivers/base/core.c:1679
netdev_register_kobject+0x183/0x360 net/core/net-sysfs.c:1603
register_netdevice+0xa27/0xed0 net/core/dev.c:7228
tun_set_iff drivers/net/tun.c:1843 [inline]
__tun_chr_ioctl+0x1bd0/0x3b70 drivers/net/tun.c:2046
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2291
vfs_ioctl fs/ioctl.c:43 [inline]
do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
SYSC_ioctl fs/ioctl.c:698 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
entry_SYSCALL_64_fastpath+0x1f/0xc2
Memory state around the buggy address:
ffff880160ef3500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff880160ef3580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff880160ef3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff880160ef3680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
ffff880160ef3700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================
I think we need:
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 5ed506d648c4..d435916f6527 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -2129,8 +2129,8 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
if (!bitmap)
return 0;
- bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
- kfree(bitmap);
+ if (!this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
+ kfree(bitmap);
}
Otherwise we both free the still installed old pointer and leak the new one.
Thanks! I don't think it's syzcaller per se that's provoking this; it's a matter of an interrupt coming in at the right time and preempting a task that happens to be allocating from an IDA with another task that's also allocating from an IDA. So any workload which makes heavy use of the kernel could provoke it. I imagine syzcaller is exercising a lot of parts of the kernel which use IDAs.
Funny that it didn't show up before now ... it's been in linux-next in this form since the start of February.
I've created a test case which will reproduce this, and after applying this patch it no longer reproduces. So I'm confident in your second patch :-)
> -----Original Message-----
> From: Dmitry Vyukov [mailto:[email protected]]
> Sent: Friday, March 3, 2017 5:06 AM
> To: Matthew Wilcox <[email protected]>; Andrew Morton
> <[email protected]>; [email protected]; Johannes Weiner
> <[email protected]>; Jan Kara <[email protected]>; LKML <linux-
> [email protected]>; Tejun Heo <[email protected]>
> Cc: syzkaller <[email protected]>
> Subject: Re: idr: use-after-free write in ida_get_new_above
>
> On Fri, Mar 3, 2017 at 10:51 AM, Dmitry Vyukov <[email protected]>
> wrote:
> > Hello,
> >
> > I am hitting the following use-after-free reports while running
> > syzkaller fuzzer on commit c82be9d2244aacea9851c86f4fb74694c99cd874:
> >
> >
> ==================================================================
> > BUG: KASAN: use-after-free in ida_get_new_above+0x564/0x9b0
> > lib/idr.c:295 at addr ffff880160ef3600
> > Write of size 128 by task syz-executor1/1757
> > CPU: 1 PID: 1757 Comm: syz-executor1 Not tainted 4.10.0+ #98
> > Hardware name: Google Google Compute Engine/Google Compute Engine,
> > BIOS Google 01/01/2011
> > Call Trace:
> > __dump_stack lib/dump_stack.c:15 [inline]
> > dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
> > kasan_object_err+0x1c/0x70 mm/kasan/report.c:162
> > print_address_description mm/kasan/report.c:200 [inline]
> > kasan_report_error mm/kasan/report.c:289 [inline]
> > kasan_report.part.2+0x1e5/0x4b0 mm/kasan/report.c:311
> > kasan_report+0x21/0x30 mm/kasan/report.c:298
> > check_memory_region_inline mm/kasan/kasan.c:315 [inline]
> > check_memory_region+0x139/0x190 mm/kasan/kasan.c:322
> > memset+0x23/0x40 mm/kasan/kasan.c:340
> > ida_get_new_above+0x564/0x9b0 lib/idr.c:295
> > ida_get_new include/linux/idr.h:209 [inline]
> > proc_alloc_inum+0x97/0x1f0 fs/proc/generic.c:201
> > proc_register+0x25/0x2f0 fs/proc/generic.c:338
> > proc_create_data+0x100/0x190 fs/proc/generic.c:509
> > proc_create include/linux/proc_fs.h:35 [inline]
> > ip_rt_do_proc_init+0x53/0x110 net/ipv4/route.c:382
> > ops_init+0x10a/0x530 net/core/net_namespace.c:115
> > setup_net+0x2ed/0x690 net/core/net_namespace.c:291
> > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
> > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
> > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
> > SYSC_unshare kernel/fork.c:2281 [inline]
> > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
> > entry_SYSCALL_64_fastpath+0x1f/0xc2
> > RIP: 0033:0x44fb79
> > RSP: 002b:00007f1b66930b58 EFLAGS: 00000212 ORIG_RAX:
> 0000000000000110
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044fb79
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062020200
> > RBP: 0000000062020200 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000212 R12: 00000000007082a0
> > R13: 0000000000000004 R14: 0000000000000400 R15: 0000000000000000
> > Object at ffff880160ef3600, in cache kmalloc-128 size: 128
> > Allocated:
> > PID = 1730
> > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
> > save_stack+0x43/0xd0 mm/kasan/kasan.c:502
> > set_track mm/kasan/kasan.c:514 [inline]
> > kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605
> > kmem_cache_alloc_trace+0x10b/0x670 mm/slab.c:3634
> > kmalloc include/linux/slab.h:490 [inline]
> > ida_pre_get+0xcd/0xe0 lib/radix-tree.c:2129
> > proc_alloc_inum+0xc5/0x1f0 fs/proc/generic.c:197
> > proc_register+0x25/0x2f0 fs/proc/generic.c:338
> > proc_create_data+0x100/0x190 fs/proc/generic.c:509
> > proc_create include/linux/proc_fs.h:35 [inline]
> > packet_net_init+0x8d/0xb0 net/packet/af_packet.c:4488
> > ops_init+0x10a/0x530 net/core/net_namespace.c:115
> > setup_net+0x2ed/0x690 net/core/net_namespace.c:291
> > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
> > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
> > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
> > SYSC_unshare kernel/fork.c:2281 [inline]
> > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
> > entry_SYSCALL_64_fastpath+0x1f/0xc2
> > Freed:
> > PID = 1648
> > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
> > save_stack+0x43/0xd0 mm/kasan/kasan.c:502
> > set_track mm/kasan/kasan.c:514 [inline]
> > kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:578
> > __cache_free mm/slab.c:3510 [inline]
> > kfree+0xd3/0x250 mm/slab.c:3827
> > ida_pre_get+0x8a/0xe0 lib/radix-tree.c:2133
> > ida_simple_get+0x168/0x320 lib/idr.c:443
> > __kernfs_new_node+0xfe/0x3c0 fs/kernfs/dir.c:633
> > kernfs_new_node+0x80/0xe0 fs/kernfs/dir.c:661
> > kernfs_create_dir_ns+0x41/0x140 fs/kernfs/dir.c:933
> > kernfs_create_dir include/linux/kernfs.h:477 [inline]
> > internal_create_group+0xf7/0x8f0 fs/sysfs/group.c:124
> > sysfs_create_group fs/sysfs/group.c:156 [inline]
> > sysfs_create_groups+0x97/0x130 fs/sysfs/group.c:183
> > device_add_groups drivers/base/core.c:1031 [inline]
> > device_add_attrs drivers/base/core.c:1058 [inline]
> > device_add+0xb2f/0x1650 drivers/base/core.c:1679
> > netdev_register_kobject+0x183/0x360 net/core/net-sysfs.c:1603
> > register_netdevice+0xa27/0xed0 net/core/dev.c:7228
> > tun_set_iff drivers/net/tun.c:1843 [inline]
> > __tun_chr_ioctl+0x1bd0/0x3b70 drivers/net/tun.c:2046
> > tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2291
> > vfs_ioctl fs/ioctl.c:43 [inline]
> > do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
> > SYSC_ioctl fs/ioctl.c:698 [inline]
> > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
> > entry_SYSCALL_64_fastpath+0x1f/0xc2
> > Memory state around the buggy address:
> > ffff880160ef3500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> > ffff880160ef3580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> >>ffff880160ef3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ^
> > ffff880160ef3680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
> > ffff880160ef3700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> >
> ==================================================================
> >
> >
> > I think we need:
> >
> > diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> > index 5ed506d648c4..d435916f6527 100644
> > --- a/lib/radix-tree.c
> > +++ b/lib/radix-tree.c
> > @@ -2129,8 +2129,8 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
> > struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
> > if (!bitmap)
> > return 0;
> > - bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
> > - kfree(bitmap);
> > + if (!this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
> > + kfree(bitmap);
>
> I meant:
>
> + if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
> + kfree(bitmap);
>
>
> > }
> >
> >
> > Otherwise we both free the still installed old pointer and leak the new one.
On Fri, Mar 3, 2017 at 10:51 AM, Dmitry Vyukov <[email protected]> wrote:
> Hello,
>
> I am hitting the following use-after-free reports while running
> syzkaller fuzzer on commit c82be9d2244aacea9851c86f4fb74694c99cd874:
>
> ==================================================================
> BUG: KASAN: use-after-free in ida_get_new_above+0x564/0x9b0
> lib/idr.c:295 at addr ffff880160ef3600
> Write of size 128 by task syz-executor1/1757
> CPU: 1 PID: 1757 Comm: syz-executor1 Not tainted 4.10.0+ #98
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:15 [inline]
> dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
> kasan_object_err+0x1c/0x70 mm/kasan/report.c:162
> print_address_description mm/kasan/report.c:200 [inline]
> kasan_report_error mm/kasan/report.c:289 [inline]
> kasan_report.part.2+0x1e5/0x4b0 mm/kasan/report.c:311
> kasan_report+0x21/0x30 mm/kasan/report.c:298
> check_memory_region_inline mm/kasan/kasan.c:315 [inline]
> check_memory_region+0x139/0x190 mm/kasan/kasan.c:322
> memset+0x23/0x40 mm/kasan/kasan.c:340
> ida_get_new_above+0x564/0x9b0 lib/idr.c:295
> ida_get_new include/linux/idr.h:209 [inline]
> proc_alloc_inum+0x97/0x1f0 fs/proc/generic.c:201
> proc_register+0x25/0x2f0 fs/proc/generic.c:338
> proc_create_data+0x100/0x190 fs/proc/generic.c:509
> proc_create include/linux/proc_fs.h:35 [inline]
> ip_rt_do_proc_init+0x53/0x110 net/ipv4/route.c:382
> ops_init+0x10a/0x530 net/core/net_namespace.c:115
> setup_net+0x2ed/0x690 net/core/net_namespace.c:291
> copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
> create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
> unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
> SYSC_unshare kernel/fork.c:2281 [inline]
> SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
> entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x44fb79
> RSP: 002b:00007f1b66930b58 EFLAGS: 00000212 ORIG_RAX: 0000000000000110
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044fb79
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062020200
> RBP: 0000000062020200 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000007082a0
> R13: 0000000000000004 R14: 0000000000000400 R15: 0000000000000000
> Object at ffff880160ef3600, in cache kmalloc-128 size: 128
> Allocated:
> PID = 1730
> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
> save_stack+0x43/0xd0 mm/kasan/kasan.c:502
> set_track mm/kasan/kasan.c:514 [inline]
> kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605
> kmem_cache_alloc_trace+0x10b/0x670 mm/slab.c:3634
> kmalloc include/linux/slab.h:490 [inline]
> ida_pre_get+0xcd/0xe0 lib/radix-tree.c:2129
> proc_alloc_inum+0xc5/0x1f0 fs/proc/generic.c:197
> proc_register+0x25/0x2f0 fs/proc/generic.c:338
> proc_create_data+0x100/0x190 fs/proc/generic.c:509
> proc_create include/linux/proc_fs.h:35 [inline]
> packet_net_init+0x8d/0xb0 net/packet/af_packet.c:4488
> ops_init+0x10a/0x530 net/core/net_namespace.c:115
> setup_net+0x2ed/0x690 net/core/net_namespace.c:291
> copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
> create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
> unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
> SYSC_unshare kernel/fork.c:2281 [inline]
> SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
> entry_SYSCALL_64_fastpath+0x1f/0xc2
> Freed:
> PID = 1648
> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
> save_stack+0x43/0xd0 mm/kasan/kasan.c:502
> set_track mm/kasan/kasan.c:514 [inline]
> kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:578
> __cache_free mm/slab.c:3510 [inline]
> kfree+0xd3/0x250 mm/slab.c:3827
> ida_pre_get+0x8a/0xe0 lib/radix-tree.c:2133
> ida_simple_get+0x168/0x320 lib/idr.c:443
> __kernfs_new_node+0xfe/0x3c0 fs/kernfs/dir.c:633
> kernfs_new_node+0x80/0xe0 fs/kernfs/dir.c:661
> kernfs_create_dir_ns+0x41/0x140 fs/kernfs/dir.c:933
> kernfs_create_dir include/linux/kernfs.h:477 [inline]
> internal_create_group+0xf7/0x8f0 fs/sysfs/group.c:124
> sysfs_create_group fs/sysfs/group.c:156 [inline]
> sysfs_create_groups+0x97/0x130 fs/sysfs/group.c:183
> device_add_groups drivers/base/core.c:1031 [inline]
> device_add_attrs drivers/base/core.c:1058 [inline]
> device_add+0xb2f/0x1650 drivers/base/core.c:1679
> netdev_register_kobject+0x183/0x360 net/core/net-sysfs.c:1603
> register_netdevice+0xa27/0xed0 net/core/dev.c:7228
> tun_set_iff drivers/net/tun.c:1843 [inline]
> __tun_chr_ioctl+0x1bd0/0x3b70 drivers/net/tun.c:2046
> tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2291
> vfs_ioctl fs/ioctl.c:43 [inline]
> do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
> SYSC_ioctl fs/ioctl.c:698 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
> entry_SYSCALL_64_fastpath+0x1f/0xc2
> Memory state around the buggy address:
> ffff880160ef3500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff880160ef3580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>>ffff880160ef3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff880160ef3680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
> ffff880160ef3700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> I think we need:
>
> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> index 5ed506d648c4..d435916f6527 100644
> --- a/lib/radix-tree.c
> +++ b/lib/radix-tree.c
> @@ -2129,8 +2129,8 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
> struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
> if (!bitmap)
> return 0;
> - bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
> - kfree(bitmap);
> + if (!this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
> + kfree(bitmap);
I meant:
+ if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
+ kfree(bitmap);
> }
>
>
> Otherwise we both free the still installed old pointer and leak the new one.
On Fri, Mar 3, 2017 at 6:06 PM, Matthew Wilcox <[email protected]> wrote:
> Thanks! I don't think it's syzcaller per se that's provoking this; it's a matter of an interrupt coming in at the right time and preempting a task that happens to be allocating from an IDA with another task that's also allocating from an IDA. So any workload which makes heavy use of the kernel could provoke it. I imagine syzcaller is exercising a lot of parts of the kernel which use IDAs.
>
> Funny that it didn't show up before now ... it's been in linux-next in this form since the start of February.
>
> I've created a test case which will reproduce this, and after applying this patch it no longer reproduces. So I'm confident in your second patch :-)
Mailed the patch:
https://groups.google.com/d/msg/syzkaller/dpZ6ou1WOiI/7zfgSe1QEAAJ
Well, it's not syzkaller alone. Also KASAN + stressing kernel +
continuously monitoring oopses.
It's not too surprising to me that it wasn't caught before. If one
doesn't use KASAN (do you?), he/she would just track random memory
corruptions for months.
>> -----Original Message-----
>> From: Dmitry Vyukov [mailto:[email protected]]
>> Sent: Friday, March 3, 2017 5:06 AM
>> To: Matthew Wilcox <[email protected]>; Andrew Morton
>> <[email protected]>; [email protected]; Johannes Weiner
>> <[email protected]>; Jan Kara <[email protected]>; LKML <linux-
>> [email protected]>; Tejun Heo <[email protected]>
>> Cc: syzkaller <[email protected]>
>> Subject: Re: idr: use-after-free write in ida_get_new_above
>>
>> On Fri, Mar 3, 2017 at 10:51 AM, Dmitry Vyukov <[email protected]>
>> wrote:
>> > Hello,
>> >
>> > I am hitting the following use-after-free reports while running
>> > syzkaller fuzzer on commit c82be9d2244aacea9851c86f4fb74694c99cd874:
>> >
>> >
>> ==================================================================
>> > BUG: KASAN: use-after-free in ida_get_new_above+0x564/0x9b0
>> > lib/idr.c:295 at addr ffff880160ef3600
>> > Write of size 128 by task syz-executor1/1757
>> > CPU: 1 PID: 1757 Comm: syz-executor1 Not tainted 4.10.0+ #98
>> > Hardware name: Google Google Compute Engine/Google Compute Engine,
>> > BIOS Google 01/01/2011
>> > Call Trace:
>> > __dump_stack lib/dump_stack.c:15 [inline]
>> > dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
>> > kasan_object_err+0x1c/0x70 mm/kasan/report.c:162
>> > print_address_description mm/kasan/report.c:200 [inline]
>> > kasan_report_error mm/kasan/report.c:289 [inline]
>> > kasan_report.part.2+0x1e5/0x4b0 mm/kasan/report.c:311
>> > kasan_report+0x21/0x30 mm/kasan/report.c:298
>> > check_memory_region_inline mm/kasan/kasan.c:315 [inline]
>> > check_memory_region+0x139/0x190 mm/kasan/kasan.c:322
>> > memset+0x23/0x40 mm/kasan/kasan.c:340
>> > ida_get_new_above+0x564/0x9b0 lib/idr.c:295
>> > ida_get_new include/linux/idr.h:209 [inline]
>> > proc_alloc_inum+0x97/0x1f0 fs/proc/generic.c:201
>> > proc_register+0x25/0x2f0 fs/proc/generic.c:338
>> > proc_create_data+0x100/0x190 fs/proc/generic.c:509
>> > proc_create include/linux/proc_fs.h:35 [inline]
>> > ip_rt_do_proc_init+0x53/0x110 net/ipv4/route.c:382
>> > ops_init+0x10a/0x530 net/core/net_namespace.c:115
>> > setup_net+0x2ed/0x690 net/core/net_namespace.c:291
>> > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
>> > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
>> > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
>> > SYSC_unshare kernel/fork.c:2281 [inline]
>> > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
>> > entry_SYSCALL_64_fastpath+0x1f/0xc2
>> > RIP: 0033:0x44fb79
>> > RSP: 002b:00007f1b66930b58 EFLAGS: 00000212 ORIG_RAX:
>> 0000000000000110
>> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044fb79
>> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062020200
>> > RBP: 0000000062020200 R08: 0000000000000000 R09: 0000000000000000
>> > R10: 0000000000000000 R11: 0000000000000212 R12: 00000000007082a0
>> > R13: 0000000000000004 R14: 0000000000000400 R15: 0000000000000000
>> > Object at ffff880160ef3600, in cache kmalloc-128 size: 128
>> > Allocated:
>> > PID = 1730
>> > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>> > save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>> > set_track mm/kasan/kasan.c:514 [inline]
>> > kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605
>> > kmem_cache_alloc_trace+0x10b/0x670 mm/slab.c:3634
>> > kmalloc include/linux/slab.h:490 [inline]
>> > ida_pre_get+0xcd/0xe0 lib/radix-tree.c:2129
>> > proc_alloc_inum+0xc5/0x1f0 fs/proc/generic.c:197
>> > proc_register+0x25/0x2f0 fs/proc/generic.c:338
>> > proc_create_data+0x100/0x190 fs/proc/generic.c:509
>> > proc_create include/linux/proc_fs.h:35 [inline]
>> > packet_net_init+0x8d/0xb0 net/packet/af_packet.c:4488
>> > ops_init+0x10a/0x530 net/core/net_namespace.c:115
>> > setup_net+0x2ed/0x690 net/core/net_namespace.c:291
>> > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396
>> > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106
>> > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205
>> > SYSC_unshare kernel/fork.c:2281 [inline]
>> > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231
>> > entry_SYSCALL_64_fastpath+0x1f/0xc2
>> > Freed:
>> > PID = 1648
>> > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>> > save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>> > set_track mm/kasan/kasan.c:514 [inline]
>> > kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:578
>> > __cache_free mm/slab.c:3510 [inline]
>> > kfree+0xd3/0x250 mm/slab.c:3827
>> > ida_pre_get+0x8a/0xe0 lib/radix-tree.c:2133
>> > ida_simple_get+0x168/0x320 lib/idr.c:443
>> > __kernfs_new_node+0xfe/0x3c0 fs/kernfs/dir.c:633
>> > kernfs_new_node+0x80/0xe0 fs/kernfs/dir.c:661
>> > kernfs_create_dir_ns+0x41/0x140 fs/kernfs/dir.c:933
>> > kernfs_create_dir include/linux/kernfs.h:477 [inline]
>> > internal_create_group+0xf7/0x8f0 fs/sysfs/group.c:124
>> > sysfs_create_group fs/sysfs/group.c:156 [inline]
>> > sysfs_create_groups+0x97/0x130 fs/sysfs/group.c:183
>> > device_add_groups drivers/base/core.c:1031 [inline]
>> > device_add_attrs drivers/base/core.c:1058 [inline]
>> > device_add+0xb2f/0x1650 drivers/base/core.c:1679
>> > netdev_register_kobject+0x183/0x360 net/core/net-sysfs.c:1603
>> > register_netdevice+0xa27/0xed0 net/core/dev.c:7228
>> > tun_set_iff drivers/net/tun.c:1843 [inline]
>> > __tun_chr_ioctl+0x1bd0/0x3b70 drivers/net/tun.c:2046
>> > tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2291
>> > vfs_ioctl fs/ioctl.c:43 [inline]
>> > do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
>> > SYSC_ioctl fs/ioctl.c:698 [inline]
>> > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
>> > entry_SYSCALL_64_fastpath+0x1f/0xc2
>> > Memory state around the buggy address:
>> > ffff880160ef3500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>> > ffff880160ef3580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> >>ffff880160ef3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> > ^
>> > ffff880160ef3680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
>> > ffff880160ef3700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>> >
>> ==================================================================
>> >
>> >
>> > I think we need:
>> >
>> > diff --git a/lib/radix-tree.c b/lib/radix-tree.c
>> > index 5ed506d648c4..d435916f6527 100644
>> > --- a/lib/radix-tree.c
>> > +++ b/lib/radix-tree.c
>> > @@ -2129,8 +2129,8 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
>> > struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
>> > if (!bitmap)
>> > return 0;
>> > - bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
>> > - kfree(bitmap);
>> > + if (!this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
>> > + kfree(bitmap);
>>
>> I meant:
>>
>> + if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
>> + kfree(bitmap);
>>
>>
>> > }
>> >
>> >
>> > Otherwise we both free the still installed old pointer and leak the new one.