KASAN: slab-out-of-bounds Read in btrfs_scan_one_device

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 521b619a Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3' ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16a55792500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e791ddf0875adf65
dashboard link: https://syzkaller.appspot.com/bug?extid=c4b1e5278d93269fd69c
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16296f5c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1614e746500000

The issue was bisected to:

commit 3831bf0094abed51e71cbeca8b6edf8b88c2644b
Author: Johannes Thumshirn <jthum...@suse.de>
Date: Mon Oct 7 09:11:02 2019 +0000

btrfs: add sha256 to checksumming algorithm

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=163a3034500000
final oops: https://syzkaller.appspot.com/x/report.txt?x=153a3034500000
console output: https://syzkaller.appspot.com/x/log.txt?x=113a3034500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c4b1e5...@syzkaller.appspotmail.com
Fixes: 3831bf0094ab ("btrfs: add sha256 to checksumming algorithm")

==================================================================
BUG: KASAN: slab-out-of-bounds in btrfs_printk+0x421/0x46b fs/btrfs/super.c:245
Read of size 8 at addr ffff8880146246a0 by task systemd-udevd/8518

CPU: 0 PID: 8518 Comm: systemd-udevd Not tainted 5.10.0-rc2-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+0x137/0x1be lib/dump_stack.c:118
print_address_description+0x6c/0x660 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_control_ioctl+0xd1/0x210 fs/btrfs/super.c:2327
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f7f94bc0017
Code: 00 00 00 48 8b 05 81 7e 2b 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 51 7e 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc3c7245f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7f94bc0017
RDX: 00007ffc3c724610 RSI: 0000000090009427 RDI: 000000000000000f
RBP: 00007ffc3c724610 R08: 0000000000000000 R09: 0000000000000018
R10: 0000000000000001 R11: 0000000000000246 R12: 000000000000000f
R13: 0000000000000000 R14: 0000564c3b1752c0 R15: 0000564c3b162060

Allocated by task 8745:
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x111/0x140 mm/kasan/common.c:461
slab_post_alloc_hook+0x3e/0x2b0 mm/slab.h:526
slab_alloc_node mm/slub.c:2891 [inline]
kmem_cache_alloc_node+0x144/0x280 mm/slub.c:2927
alloc_unbound_pwq+0x591/0x1060 kernel/workqueue.c:3801
apply_wqattrs_prepare+0x3d2/0xcb0 kernel/workqueue.c:3946
apply_workqueue_attrs_locked+0xcd/0x7b0 kernel/workqueue.c:4029
apply_workqueue_attrs kernel/workqueue.c:4066 [inline]
alloc_and_link_pwqs kernel/workqueue.c:4190 [inline]
alloc_workqueue+0xe7e/0x1480 kernel/workqueue.c:4298
__btrfs_alloc_workqueue+0x181/0x2d0 fs/btrfs/async-thread.c:108
btrfs_alloc_workqueue+0x8c/0x1b0 fs/btrfs/async-thread.c:140
btrfs_init_workqueues fs/btrfs/disk-io.c:2162 [inline]
open_ctree+0x1243/0x3b3b fs/btrfs/disk-io.c:3088
btrfs_fill_super fs/btrfs/super.c:1316 [inline]
btrfs_mount_root+0x9b8/0xb60 fs/btrfs/super.c:1672
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+0x17b4/0x2a20 fs/namespace.c:3205
do_mount fs/namespace.c:3218 [inline]
__do_sys_mount fs/namespace.c:3426 [inline]
__se_sys_mount+0x28c/0x320 fs/namespace.c:3403
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 ffff888014624400
which belongs to the cache pool_workqueue of size 512
The buggy address is located 160 bytes to the right of
512-byte region [ffff888014624400, ffff888014624600)
The buggy address belongs to the page:
page:000000006b59311c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14624
head:000000006b59311c order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff88801044dc80
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888014624580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888014624600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888014624680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff888014624700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888014624780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[syzbot]

syzbot suspects this issue was fixed by commit:

commit 0697d9a610998b8bdee6b2390836cb2391d8fd1a
Author: Johannes Thumshirn <johannes....@wdc.com>
Date: Wed Nov 18 09:03:26 2020 +0000

btrfs: don't access possibly stale fs_info data for printing duplicate device

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10fb0d9b500000
start commit: 521b619a Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3' ..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=e791ddf0875adf65
dashboard link: https://syzkaller.appspot.com/bug?extid=c4b1e5278d93269fd69c

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16296f5c500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1614e746500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: btrfs: don't access possibly stale fs_info data for printing duplicate device

[Dmitry Vyukov]