[v6.6] KASAN: use-after-free Read in search_by_entry_key

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9760bf04666d Linux 6.6.135
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=155331ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=9e7dd320c1887f1d74a8
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a685913d05a7/disk-9760bf04.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a3c1d21d4bca/vmlinux-9760bf04.xz
kernel image: https://storage.googleapis.com/syzbot-assets/09178887ef0d/bzImage-9760bf04.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9e7dd3...@syzkaller.appspotmail.com

REISERFS warning (device loop3): vs-13060 reiserfs_update_sd_size: stat data of object [3 6 0x0 SD] (nlink == 2) not found (pos 1)
==================================================================
BUG: KASAN: use-after-free in bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
BUG: KASAN: use-after-free in search_by_entry_key+0x59e/0xd60 fs/reiserfs/namei.c:165
Read of size 4 at addr ffff88805218cfc4 by task syz.3.807/8889

CPU: 0 PID: 8889 Comm: syz.3.807 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
search_by_entry_key+0x59e/0xd60 fs/reiserfs/namei.c:165
reiserfs_find_entry+0x2e9/0x1340 fs/reiserfs/namei.c:322
reiserfs_lookup+0x1dc/0x580 fs/reiserfs/namei.c:368
__lookup_slow+0x2a1/0x400 fs/namei.c:1702
lookup_one_len+0x1a1/0x2e0 fs/namei.c:2752
open_xa_dir+0x468/0x700 fs/reiserfs/xattr.c:163
xattr_lookup+0x22/0x2a0 fs/reiserfs/xattr.c:396
reiserfs_xattr_set_handle+0x106/0xd70 fs/reiserfs/xattr.c:535
reiserfs_xattr_set+0x46b/0x590 fs/reiserfs/xattr.c:635
__vfs_setxattr+0x431/0x470 fs/xattr.c:201
__vfs_setxattr_noperm+0x12d/0x5e0 fs/xattr.c:235
vfs_setxattr+0x16b/0x2f0 fs/xattr.c:322
do_setxattr fs/xattr.c:630 [inline]
path_setxattr+0x3f3/0x5d0 fs/xattr.c:659
__do_sys_lsetxattr fs/xattr.c:684 [inline]
__se_sys_lsetxattr fs/xattr.c:680 [inline]
__x64_sys_lsetxattr+0xb8/0xd0 fs/xattr.c:680
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f21cf39c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f21d0233028 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
RAX: ffffffffffffffda RBX: 00007f21cf615fa0 RCX: 00007f21cf39c819
RDX: 0000000000000000 RSI: 0000200000002080 RDI: 0000200000001180
RBP: 00007f21cf432c91 R08: 0000000000000003 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f21cf616038 R14: 00007f21cf615fa0 R15: 00007ffe254987d8
</TASK>

The buggy address belongs to the physical page:
page:ffffea0001486300 refcount:1 mapcount:0 mapping:ffff88806a3cac20 index:0x2f1e pfn:0x5218c
memcg:ffff888079672000
aops:shmem_aops ino:454 dentry name(?):"memfd:syzkaller"
flags: 0xfff6000008003c(referenced|uptodate|dirty|lru|swapbacked|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff6000008003c ffffea00014862c8 ffffea0001486348 ffff88806a3cac20
raw: 0000000000002f1e 0000000000000000 00000001ffffffff ffff888079672000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 8894, tgid 8893 (syz.5.808), ts 248144895749, free_ts 236445541228
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
prep_new_page mm/page_alloc.c:1588 [inline]
get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
__folio_alloc+0x10/0x20 mm/page_alloc.c:4532
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2240
shmem_alloc_folio+0x1a9/0x2a0 mm/shmem.c:1679
shmem_alloc_and_acct_folio+0x1e6/0x6d0 mm/shmem.c:1704
shmem_get_folio_gfp+0xcde/0x2aa0 mm/shmem.c:2041
shmem_get_folio mm/shmem.c:2164 [inline]
shmem_write_begin+0xf2/0x420 mm/shmem.c:2706
generic_perform_write+0x2fe/0x5c0 mm/filemap.c:4036
shmem_file_write_iter+0xfb/0x120 mm/shmem.c:2883
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x46c/0x990 fs/read_write.c:584
ksys_write+0x150/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1181 [inline]
free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2504
release_pages+0x1f7a/0x2200 mm/swap.c:1022
__folio_batch_release+0x71/0xe0 mm/swap.c:1042
folio_batch_release include/linux/pagevec.h:83 [inline]
shmem_undo_range+0x630/0x1b20 mm/shmem.c:1026
shmem_truncate_range mm/shmem.c:1135 [inline]
shmem_evict_inode+0x245/0x9e0 mm/shmem.c:1264
evict+0x4ca/0x8d0 fs/inode.c:705
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
task_work_run+0x1d4/0x260 kernel/task_work.c:245
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82

Memory state around the buggy address:
ffff88805218ce80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805218cf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805218cf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff88805218d000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805218d080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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