[moderation] [ocfs2?] KASAN: use-after-free Read in ocfs2_dx_dir_lookup_rec

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 46a51f4f5eda Merge tag 'for-v6.17-rc' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10fb0534580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=d94c57a84f7386db1fbd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [jl...@evilplan.org jose...@linux.alibaba.com linux-...@vger.kernel.org ma...@fasheh.com ocfs2...@lists.linux.dev]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-46a51f4f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ccc826c963ac/vmlinux-46a51f4f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/79f8a247dcf5/bzImage-46a51f4f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d94c57...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
=======================================================
WARNING: The mand mount option has been deprecated and
and is ignored by this kernel. Remove the mand
option from the mount to silence this warning.
=======================================================
JBD2: Ignoring recovery information on journal
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
(syz.0.0,5362,0):ocfs2_check_set_options:1244 ERROR: Invalid heartbeat mount options
loop0: detected capacity change from 32768 to 32767
OCFS2: ERROR (device loop0): int ocfs2_validate_dx_root(struct super_block *, struct buffer_head *): Dir Index Root # 0 has bad signature
On-disk corruption discovered. Please run fsck.ocfs2 once the filesystem is unmounted.
OCFS2: File system is now read-only.
(syz.0.0,5362,0):ocfs2_find_entry_dx:1037 ERROR: status = -30
==================================================================
BUG: KASAN: use-after-free in ocfs2_dx_dir_lookup_rec+0x1eb/0x7f0 fs/ocfs2/dir.c:813
Read of size 4 at addr ffff888053a16cc0 by task syz.0.0/5362

CPU: 0 UID: 0 PID: 5362 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
ocfs2_dx_dir_lookup_rec+0x1eb/0x7f0 fs/ocfs2/dir.c:813
ocfs2_dx_dir_lookup+0xdb/0x520 fs/ocfs2/dir.c:868
ocfs2_dx_dir_search fs/ocfs2/dir.c:928 [inline]
ocfs2_find_entry_dx fs/ocfs2/dir.c:1042 [inline]
ocfs2_find_entry+0x1004/0x2000 fs/ocfs2/dir.c:1079
ocfs2_check_dir_for_entry+0x14c/0x3f0 fs/ocfs2/dir.c:2048
ocfs2_mknod+0x697/0x2050 fs/ocfs2/namei.c:291
ocfs2_create+0x1a5/0x440 fs/ocfs2/namei.c:676
lookup_open fs/namei.c:3708 [inline]
open_last_lookups fs/namei.c:3807 [inline]
path_openat+0x14f1/0x3830 fs/namei.c:4043
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1461
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4f0218eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4f030d3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4f023d5fa0 RCX: 00007f4f0218eba9
RDX: 0000000000105042 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f4f02211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000001ff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4f023d6038 R14: 00007f4f023d5fa0 R15: 00007ffd398b73c8
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x45 pfn:0x53a16
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 ffffea00014e8548 ffffea00014e85c8 0000000000000000
raw: 0000000000000045 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 5362, tgid 5361 (syz.0.0), ts 89016941703, free_ts 89264881276
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2435
shmem_alloc_folio mm/shmem.c:1908 [inline]
shmem_alloc_and_add_folio+0x447/0xf60 mm/shmem.c:1947
shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2597
shmem_get_folio mm/shmem.c:2703 [inline]
shmem_write_begin+0xf7/0x2b0 mm/shmem.c:3353
generic_perform_write+0x2c2/0x900 mm/filemap.c:4175
shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3528
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5362 tgid 5361 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
free_unref_folios+0xdbd/0x1520 mm/page_alloc.c:2952
folios_put_refs+0x559/0x640 mm/swap.c:997
folio_batch_release include/linux/pagevec.h:101 [inline]
shmem_undo_range+0x49e/0x14b0 mm/shmem.c:1157
shmem_truncate_range mm/shmem.c:1269 [inline]
shmem_evict_inode+0x272/0xa70 mm/shmem.c:1397
evict+0x501/0x9c0 fs/inode.c:810
__dentry_kill+0x209/0x660 fs/dcache.c:669
dput+0x19f/0x2b0 fs/dcache.c:911
__fput+0x68e/0xa70 fs/file_table.c:476
fput_close_sync+0x119/0x200 fs/file_table.c:573
__do_sys_close fs/open.c:1587 [inline]
__se_sys_close fs/open.c:1572 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1572
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888053a16b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888053a16c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888053a16c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff888053a16d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888053a16d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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