KASAN: use-after-free Read in btrfs_scan_one_device

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: eb5f95f1 Merge tag 's390-5.9-6' of git://git.kernel.org/pu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10a0a8bb900000
kernel config: https://syzkaller.appspot.com/x/.config?x=ffe85b197a57c180
dashboard link: https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
compiler: gcc (GCC) 10.1.0-syz 20200507

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: syzbot+582e66...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in btrfs_printk+0x38b/0x40c fs/btrfs/super.c:245
Read of size 8 at addr ffff8880637006a8 by task syz-executor.2/15287

CPU: 1 PID: 15287 Comm: syz-executor.2 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x198/0x1fd lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
btrfs_printk+0x38b/0x40c fs/btrfs/super.c:245
device_list_add.cold+0x58/0x2d2 fs/btrfs/volumes.c:943
btrfs_scan_one_device+0x339/0x4a0 fs/btrfs/volumes.c:1359
btrfs_mount_root+0x4d5/0xbb0 fs/btrfs/super.c:1634
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1008
vfs_kern_mount+0x3c/0x60 fs/namespace.c:995
btrfs_mount+0x234/0xaa0 fs/btrfs/super.c:1732
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1387/0x20a0 fs/namespace.c:3192
do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]
__se_sys_mount fs/namespace.c:3390 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x46004a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 da 89 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f50d2ce8a88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f50d2ce8b20 RCX: 000000000046004a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f50d2ce8ae0
RBP: 00007f50d2ce8ae0 R08: 00007f50d2ce8b20 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000000
R13: 0000000020000100 R14: 0000000020001d40 R15: 0000000020000040

Allocated by task 15246:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
kmalloc_node include/linux/slab.h:577 [inline]
kvmalloc_node+0xb4/0xf0 mm/util.c:574
kvmalloc include/linux/mm.h:757 [inline]
kvzalloc include/linux/mm.h:765 [inline]
btrfs_mount_root+0x117/0xbb0 fs/btrfs/super.c:1613
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1008
vfs_kern_mount+0x3c/0x60 fs/namespace.c:995
btrfs_mount+0x234/0xaa0 fs/btrfs/super.c:1732
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1387/0x20a0 fs/namespace.c:3192
do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]
__se_sys_mount fs/namespace.c:3390 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 15246:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x10e/0x2b0 mm/slab.c:3756
kvfree+0x42/0x50 mm/util.c:603
deactivate_locked_super+0x94/0x160 fs/super.c:335
btrfs_mount_root+0x772/0xbb0 fs/btrfs/super.c:1678
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1008
vfs_kern_mount+0x3c/0x60 fs/namespace.c:995
btrfs_mount+0x234/0xaa0 fs/btrfs/super.c:1732
legacy_get_tree+0x105/0x220 fs/fs_context.c:592
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1387/0x20a0 fs/namespace.c:3192
do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]
__se_sys_mount fs/namespace.c:3390 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888063700000
which belongs to the cache kmalloc-16k of size 16384
The buggy address is located 1704 bytes inside of
16384-byte region [ffff888063700000, ffff888063704000)
The buggy address belongs to the page:
page:00000000e0472e19 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x63700
head:00000000e0472e19 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00024a4c08 ffffea000150ce08 ffff8880aa040b00
raw: 0000000000000000 ffff888063700000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888063700580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888063700600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888063700680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888063700700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888063700780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 325d0eab Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1512df53900000
kernel config: https://syzkaller.appspot.com/x/.config?x=6a8a2ae52ed737db
dashboard link: https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12366f8b900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14e6929b900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+582e66...@syzkaller.appspotmail.com

==================================================================

BUG: KASAN: use-after-free in btrfs_printk+0x3eb/0x435 fs/btrfs/super.c:245
Read of size 8 at addr ffff8880878e06a8 by task syz-executor225/7068

CPU: 1 PID: 7068 Comm: syz-executor225 Not tainted 5.9.0-rc5-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]

dump_stack+0x1d6/0x29e lib/dump_stack.c:118
print_address_description+0x66/0x620 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
btrfs_printk+0x3eb/0x435 fs/btrfs/super.c:245
device_list_add+0x1a88/0x1d60 fs/btrfs/volumes.c:943
btrfs_scan_one_device+0x196/0x490 fs/btrfs/volumes.c:1359
btrfs_mount_root+0x48f/0xb60 fs/btrfs/super.c:1634
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008
btrfs_mount+0x33c/0xae0 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x179d/0x29e0 fs/namespace.c:3192

do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]

__se_sys_mount+0x126/0x180 fs/namespace.c:3390
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x44840a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 cd a2 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 aa a2 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffedfffd608 EFLAGS: 00000293 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffedfffd670 RCX: 000000000044840a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffedfffd630
RBP: 00007ffedfffd630 R08: 00007ffedfffd670 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 000000000000001a
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003

Allocated by task 6945:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x100/0x130 mm/kasan/common.c:461
kmalloc_node include/linux/slab.h:577 [inline]
kvmalloc_node+0x81/0x110 mm/util.c:574

kvmalloc include/linux/mm.h:757 [inline]
kvzalloc include/linux/mm.h:765 [inline]

btrfs_mount_root+0xd0/0xb60 fs/btrfs/super.c:1613
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008
btrfs_mount+0x33c/0xae0 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x179d/0x29e0 fs/namespace.c:3192

do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]

__se_sys_mount+0x126/0x180 fs/namespace.c:3390
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6945:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xdd/0x110 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x113/0x200 mm/slab.c:3756
deactivate_locked_super+0xa7/0xf0 fs/super.c:335
btrfs_mount_root+0x72b/0xb60 fs/btrfs/super.c:1678
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008
btrfs_mount+0x33c/0xae0 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1547
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x179d/0x29e0 fs/namespace.c:3192

do_mount fs/namespace.c:3205 [inline]
__do_sys_mount fs/namespace.c:3413 [inline]

__se_sys_mount+0x126/0x180 fs/namespace.c:3390
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880878e0000

which belongs to the cache kmalloc-16k of size 16384
The buggy address is located 1704 bytes inside of

16384-byte region [ffff8880878e0000, ffff8880878e4000)

The buggy address belongs to the page:

page:0000000060704f30 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x878e0
head:0000000060704f30 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00028e9a08 ffffea00021e3608 ffff8880aa440b00
raw: 0000000000000000 ffff8880878e0000 0000000100000001 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff8880878e0580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880878e0600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880878e0680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880878e0700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880878e0780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

[Johannes Thumshirn]

Could reporoduce this one, working on it

[Johannes Thumshirn]

On 21/09/2020 07:38, syzbot wrote:

#syz test: btrfs: Fix missing close devices

[syzbot]

want 2 args (repo, branch), got 5

[syzbot]

want 2 args (repo, branch), got 5

>

> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bug...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/SN4PR0401MB3598EE548546274CFDD618AA9B3A0%40SN4PR0401MB3598.namprd04.prod.outlook.com.

[David Sterba]

On Sun, Sep 20, 2020 at 07:12:14AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: eb5f95f1 Merge tag 's390-5.9-6' of git://git.kernel.org/pu..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10a0a8bb900000
> kernel config: https://syzkaller.appspot.com/x/.config?x=ffe85b197a57c180
> dashboard link: https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
> compiler: gcc (GCC) 10.1.0-syz 20200507
>
> 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: syzbot+582e66...@syzkaller.appspotmail.com

#syz fix: btrfs: fix overflow when copying corrupt csums for a message

[David Sterba]

Johannes spotted that this is not the right fix for this report, I don't
know how to tell syzbot to revert the 'fix:' command, there isn't
'unfix' (like there's 'undup').

[Dmitry Vyukov]

Hi David,

I've added "unfix" command:
https://github.com/google/syzkaller/pull/2156

Let's give it a try:
#syz unfix

Thanks

[Dmitry Vyukov]

Voilà! Unfixed:
https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0

[David Sterba]

Thanks!

[Rustam Kovhaev]

> > Voilà! Unfixed:
> > https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
>
> Thanks!

the problem is that btrfs_kill_super() frees *fs_info while it is still
being referenced by btrfs_scan_one_device() on behalf of another
concurrent mount syscall
a very simple and dumb fix is to remove that printk that references
*fs_info:
https://syzkaller.appspot.com/text?tag=Patch&x=123537fb900000
but instead, i think proper synchronization is needed here
any advice or pointers would be highly appreciated
tyvm!

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in btrfs_scan_one_device

==================================================================
BUG: KASAN: use-after-free in btrfs_printk+0x421/0x46b fs/btrfs/super.c:245
Read of size 8 at addr ffff888027fb86a0 by task syz-executor.5/8617

CPU: 1 PID: 8617 Comm: syz-executor.5 Not tainted 5.9.0-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d6/0x29e lib/dump_stack.c:118

print_address_description+0x6c/0x640 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report+0x136/0x1e0 mm/kasan/report.c:562
btrfs_printk+0x421/0x46b fs/btrfs/super.c:245
device_list_add+0x1a94/0x1d60 fs/btrfs/volumes.c:943
btrfs_scan_one_device+0x2e1/0x460 fs/btrfs/volumes.c:1366
btrfs_mount_root+0x46e/0xb60 fs/btrfs/super.c:1634
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549

fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008

btrfs_mount+0x345/0xa80 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1799/0x29f0 fs/namespace.c:3203
do_mount fs/namespace.c:3216 [inline]
__do_sys_mount fs/namespace.c:3424 [inline]
__se_sys_mount+0x28c/0x320 fs/namespace.c:3401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4608aa
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 ad 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 8a 89 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f66fd621a88 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f66fd621b20 RCX: 00000000004608aa
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f66fd621ae0
RBP: 00007f66fd621ae0 R08: 00007f66fd621b20 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000000
R13: 0000000020000100 R14: 0000000020000200 R15: 0000000020016800

Allocated by task 8554:

kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track mm/kasan/common.c:56 [inline]

__kasan_kmalloc+0x10e/0x140 mm/kasan/common.c:461
kmalloc_node include/linux/slab.h:577 [inline]
kvmalloc_node+0x81/0xf0 mm/util.c:575
kvmalloc include/linux/mm.h:765 [inline]
kvzalloc include/linux/mm.h:773 [inline]
btrfs_mount_root+0xd1/0xb60 fs/btrfs/super.c:1613
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549

fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008

btrfs_mount+0x345/0xa80 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1799/0x29f0 fs/namespace.c:3203
do_mount fs/namespace.c:3216 [inline]
__do_sys_mount fs/namespace.c:3424 [inline]
__se_sys_mount+0x28c/0x320 fs/namespace.c:3401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 8554:

kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355

__kasan_slab_free+0xe8/0x120 mm/kasan/common.c:422
__cache_free mm/slab.c:3420 [inline]
kfree+0x124/0x210 mm/slab.c:3758
deactivate_locked_super+0xa7/0xf0 fs/super.c:335
btrfs_mount_root+0x70e/0xb60 fs/btrfs/super.c:1678
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549

fc_mount fs/namespace.c:978 [inline]
vfs_kern_mount+0xc9/0x160 fs/namespace.c:1008

btrfs_mount+0x345/0xa80 fs/btrfs/super.c:1732
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x88/0x270 fs/super.c:1549
do_new_mount fs/namespace.c:2875 [inline]
path_mount+0x1799/0x29f0 fs/namespace.c:3203
do_mount fs/namespace.c:3216 [inline]
__do_sys_mount fs/namespace.c:3424 [inline]
__se_sys_mount+0x28c/0x320 fs/namespace.c:3401
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888027fb8000

which belongs to the cache kmalloc-16k of size 16384

The buggy address is located 1696 bytes inside of
16384-byte region [ffff888027fb8000, ffff888027fbc000)

The buggy address belongs to the page:

page:00000000d102b51c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27fb8
head:00000000d102b51c order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00010d4408 ffffea0000e35408 ffff88800ec40b00
raw: 0000000000000000 ffff888027fb8000 0000000100000001 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff888027fb8580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027fb8600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027fb8680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888027fb8700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027fb8780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 9d9af100 Merge tag 'perf-tools-for-v5.10-2020-10-15' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=100be3f0500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1db8d98682d0c6c
dashboard link: https://syzkaller.appspot.com/bug?extid=582e66e5edf36a22c7b0
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)