Re: [syzbot] KFENCE: use-after-free in kmem_cache_destroy

[Dmitry Vyukov <dvyukov@google.com>]

On Mon, May 3, 2021 at 10:24 AM syzbot
<syzbot+9d90dad32dd9727ed084@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15f19ca5d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=53fdf14defd48c56
> dashboard link: https://syzkaller.appspot.com/bug?extid=9d90dad32dd9727ed084
> compiler:       Debian clang version 11.0.1-2
>
> 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+9d90dad32dd9727ed084@syzkaller.appspotmail.com

This looks like a bug in F2FS.
Interestingly this was detected by ARM MTE before but was
mis-root-caused I think:
https://lore.kernel.org/lkml/0000000000008d396205b9e4adee@google.com/
This can't be detected by KASAN directly because it doesn't instrument
mm/slab*. This can only be detected by MTE/KFENCE.


> ==================================================================
> BUG: KFENCE: use-after-free write in kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:486
>
> Use-after-free write at 0xffff88823bc16040 (in kfence-#10):
>  kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:486
>  f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869
>  f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945
>  mount_bdev+0x26c/0x3a0 fs/super.c:1367
>  legacy_get_tree+0xea/0x180 fs/fs_context.c:592
>  vfs_get_tree+0x86/0x270 fs/super.c:1497
>  do_new_mount fs/namespace.c:2905 [inline]
>  path_mount+0x196f/0x2be0 fs/namespace.c:3235
>  do_mount fs/namespace.c:3248 [inline]
>  __do_sys_mount fs/namespace.c:3456 [inline]
>  __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
>  do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> kfence-#10 [0xffff88823bc16000-0xffff88823bc160df, size=224, cache=kmem_cache] allocated by task 15453:
>  kmem_cache_zalloc include/linux/slab.h:676 [inline]
>  create_cache mm/slab_common.c:247 [inline]
>  kmem_cache_create_usercopy+0x12a/0x2f0 mm/slab_common.c:350
>  kmem_cache_create+0xf/0x20 mm/slab_common.c:405
>  f2fs_kmem_cache_create fs/f2fs/f2fs.h:2463 [inline]
>  f2fs_recover_fsync_data+0x1f0/0x8380 fs/f2fs/recovery.c:790
>  f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945
>  mount_bdev+0x26c/0x3a0 fs/super.c:1367
>  legacy_get_tree+0xea/0x180 fs/fs_context.c:592
>  vfs_get_tree+0x86/0x270 fs/super.c:1497
>  do_new_mount fs/namespace.c:2905 [inline]
>  path_mount+0x196f/0x2be0 fs/namespace.c:3235
>  do_mount fs/namespace.c:3248 [inline]
>  __do_sys_mount fs/namespace.c:3456 [inline]
>  __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
>  do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> freed by task 15448:
>  kobject_cleanup+0x1c9/0x280 lib/kobject.c:705
>  shutdown_cache mm/slab_common.c:463 [inline]
>  kmem_cache_destroy+0x93/0x120 mm/slab_common.c:492
>  f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869
>  f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945
>  mount_bdev+0x26c/0x3a0 fs/super.c:1367
>  legacy_get_tree+0xea/0x180 fs/fs_context.c:592
>  vfs_get_tree+0x86/0x270 fs/super.c:1497
>  do_new_mount fs/namespace.c:2905 [inline]
>  path_mount+0x196f/0x2be0 fs/namespace.c:3235
>  do_mount fs/namespace.c:3248 [inline]
>  __do_sys_mount fs/namespace.c:3456 [inline]
>  __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
>  do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> CPU: 0 PID: 15453 Comm: syz-executor.0 Not tainted 5.12.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:488
> Code: 0f 1f 84 00 00 00 00 00 0f 1f 00 48 85 ff 0f 84 09 01 00 00 41 57 41 56 53 48 89 fb 48 c7 c7 b8 07 dc 8c 31 f6 e8 b1 c3 00 08 <ff> 4b 40 0f 85 c0 00 00 00 48 89 df e8 20 a2 14 00 48 89 df e8 18
> RSP: 0018:ffffc900030af320 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffff88823bc16000 RCX: 0000000000000001
> RDX: 0000000000000001 RSI: 0000000000000008 RDI: 0000000000000001
> RBP: ffffc900030af870 R08: dffffc0000000000 R09: fffffbfff19b80f8
> R10: fffffbfff19b80f8 R11: 0000000000000000 R12: ffff88808c3a4000
> R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff92000615eb0
> FS:  00007f60a5228700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff88823bc16040 CR3: 000000001ccd8000 CR4: 00000000001526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869
>  f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945
>  mount_bdev+0x26c/0x3a0 fs/super.c:1367
>  legacy_get_tree+0xea/0x180 fs/fs_context.c:592
>  vfs_get_tree+0x86/0x270 fs/super.c:1497
>  do_new_mount fs/namespace.c:2905 [inline]
>  path_mount+0x196f/0x2be0 fs/namespace.c:3235
>  do_mount fs/namespace.c:3248 [inline]
>  __do_sys_mount fs/namespace.c:3456 [inline]
>  __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
>  do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x467b1a
> Code: 48 c7 c2 bc ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f60a5227fa8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 0000000000467b1a
> RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f60a5228000
> RBP: 00007f60a5228040 R08: 00007f60a5228040 R09: 0000000020000000
> R10: 0000000000000000 R11: 0000000000000206 R12: 0000000020000000
> R13: 0000000020000100 R14: 00007f60a5228000 R15: 0000000020014b00
> ==================================================================
>
>
> ---
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