[v5.15] KASAN: use-after-free Read in ocfs2_find_entry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14b4919a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e6ed99963d6ee1d
dashboard link: https://syzkaller.appspot.com/bug?extid=1fcbe1fc868c6ebac6c9
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/900f9b9bd850/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e089a5019a6/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b319f477b907/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1fcbe1...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in ocfs2_dx_dir_search fs/ocfs2/dir.c:952 [inline]
BUG: KASAN: use-after-free in ocfs2_find_entry_dx fs/ocfs2/dir.c:1034 [inline]
BUG: KASAN: use-after-free in ocfs2_find_entry+0x1370/0x1f90 fs/ocfs2/dir.c:1071
Read of size 4 at addr ffff88806892e008 by task syz.3.194/5758

CPU: 0 PID: 5758 Comm: syz.3.194 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
ocfs2_dx_dir_search fs/ocfs2/dir.c:952 [inline]
ocfs2_find_entry_dx fs/ocfs2/dir.c:1034 [inline]
ocfs2_find_entry+0x1370/0x1f90 fs/ocfs2/dir.c:1071
ocfs2_find_files_on_disk+0xdb/0x2f0 fs/ocfs2/dir.c:1995
ocfs2_lookup_ino_from_name+0x4f/0xf0 fs/ocfs2/dir.c:2017
ocfs2_lookup+0x241/0x930 fs/ocfs2/namei.c:122
lookup_open fs/namei.c:3448 [inline]
open_last_lookups fs/namei.c:3540 [inline]
path_openat+0x1003/0x2f30 fs/namei.c:3747
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f03156b3749
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:00007f031391a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f0315909fa0 RCX: 00007f03156b3749
RDX: 000000000000275a RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f0315737f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f031590a038 R14: 00007f0315909fa0 R15: 00007ffd1914e1e8
</TASK>

The buggy address belongs to the page:
page:ffffea0001a24b80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6892e
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001602888 ffffea00015107c8 0000000000000000
raw: 0000000000000001 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 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 5777, ts 123154774949, free_ts 123327824958
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
__alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
alloc_pages_vma+0x393/0x7c0 mm/mempolicy.c:2146
wp_page_copy+0x235/0x1fd0 mm/memory.c:3056
handle_pte_fault mm/memory.c:4668 [inline]
__handle_mm_fault mm/memory.c:4785 [inline]
handle_mm_fault+0x1ec7/0x43b0 mm/memory.c:4883
do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
handle_page_fault arch/x86/mm/fault.c:1445 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
release_pages+0x184b/0x1bb0 mm/swap.c:963
tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
tlb_flush_mmu mm/mmu_gather.c:247 [inline]
tlb_finish_mmu+0x164/0x2e0 mm/mmu_gather.c:338
exit_mmap+0x3a6/0x5f0 mm/mmap.c:3218
__mmput+0x115/0x3b0 kernel/fork.c:1127
exit_mm+0x567/0x6c0 kernel/exit.c:550
do_exit+0x5a1/0x20a0 kernel/exit.c:870
do_group_exit+0x12e/0x300 kernel/exit.c:997
__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
ffff88806892df00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88806892df80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88806892e000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88806892e080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806892e100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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