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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 51a24b7deaae Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1531fd34580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=30b53487d00b4f7f0922
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14263f12580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14a8f142580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-51a24b7d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2d2422223a2d/vmlinux-51a24b7d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3f33b7e0feca/bzImage-51a24b7d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/8f3233dafc3f/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=16b3aae2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+30b534...@syzkaller.appspotmail.com

On-disk corruption discovered. Please run fsck.ocfs2 once the filesystem is unmounted.
OCFS2: File system is now read-only.
(syz.0.17,5501,0):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 ffff88804cddc2c0 by task syz.0.17/5501

CPU: 0 UID: 0 PID: 5501 Comm: syz.0.17 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+0x14f4/0x3830 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: 0033:0x7f01a478eec9
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:00007ffe14ee92e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f01a49e5fa0 RCX: 00007f01a478eec9
RDX: 0000000000105042 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f01a4811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000001ff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f01a49e5fa0 R14: 00007f01a49e5fa0 R15: 0000000000000004
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7f45e8d66 pfn:0x4cddc
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 ffffea0001337748 ffffea00013376c8 0000000000000000
raw: 00000007f45e8d66 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 5347, tgid 5347 (syz-executor), ts 83789570758, free_ts 89515838215
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 mm/mempolicy.c:2435 [inline]
vma_alloc_folio_noprof+0xe4/0x200 mm/mempolicy.c:2470
folio_prealloc+0x30/0x180 mm/memory.c:-1
alloc_anon_folio mm/memory.c:4997 [inline]
do_anonymous_page mm/memory.c:5054 [inline]
do_pte_missing mm/memory.c:4232 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault+0x2ab9/0x5440 mm/memory.c:6195
handle_mm_fault+0x40a/0x8e0 mm/memory.c:6364
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5347 tgid 5347 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:999
free_pages_and_swap_cache+0x277/0x520 mm/swap_state.c:264
__tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
vms_clear_ptes+0x42c/0x540 mm/vma.c:1235
vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1277
do_vmi_align_munmap+0x358/0x420 mm/vma.c:1536
do_vmi_munmap+0x253/0x2e0 mm/vma.c:1584
__vm_munmap+0x23b/0x3d0 mm/vma.c:3155
__do_sys_munmap mm/mmap.c:1080 [inline]
__se_sys_munmap mm/mmap.c:1077 [inline]
__x64_sys_munmap+0x60/0x70 mm/mmap.c:1077
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:
ffff88804cddc180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88804cddc200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88804cddc280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88804cddc300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88804cddc380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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Subject: #syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e5f0a698b34ed76002dc5cff3804a61c80233a7a
Author: dman...@yandex.ru

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e5f0a698b34ed76002dc5cff3804a61c80233a7a

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+30b534...@syzkaller.appspotmail.com
Tested-by: syzbot+30b534...@syzkaller.appspotmail.com

Tested on:

commit: e5f0a698 Linux 6.17
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10261ae2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=30b53487d00b4f7f0922
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=1540ff12580000

Note: testing is done by a robot and is best-effort only.