[syzbot] [ocfs2?] KASAN: use-after-free Read in ocfs2_check_dir_entry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cfd4039213e7 Merge tag 'io_uring-6.19-20251208' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=149b5992580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8750900a7c493a0b
dashboard link: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
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=16f1aec2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17e32a1a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/57e430560492/disk-cfd40392.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9d30cdb15e4b/vmlinux-cfd40392.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ea35480882e2/bzImage-cfd40392.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/494d52f48e7a/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=12f1aec2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c89782...@syzkaller.appspotmail.com

(kworker/u8:17,3565,1):ocfs2_read_blocks_sync:112 ERROR: status = -12
(kworker/u8:17,3565,1):ocfs2_read_locked_inode:599 ERROR: status = -12
==================================================================
BUG: KASAN: use-after-free in ocfs2_check_dir_entry+0x3a0/0x480 fs/ocfs2/dir.c:318
Read of size 2 at addr ffff888052e81780 by task kworker/u8:17/3565

CPU: 1 UID: 0 PID: 3565 Comm: kworker/u8:17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: ocfs2_wq ocfs2_complete_recovery
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_check_dir_entry+0x3a0/0x480 fs/ocfs2/dir.c:318
ocfs2_dir_foreach_blk_id fs/ocfs2/dir.c:1826 [inline]
ocfs2_dir_foreach_blk+0xfff/0x1420 fs/ocfs2/dir.c:1954
ocfs2_dir_foreach+0x42/0x70 fs/ocfs2/dir.c:1965
ocfs2_queue_orphans fs/ocfs2/journal.c:2215 [inline]
ocfs2_recover_orphans fs/ocfs2/journal.c:2299 [inline]
ocfs2_complete_recovery+0xc37/0x20b0 fs/ocfs2/journal.c:1366
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x5c2 pfn:0x52e81
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea00014ba088 ffffea00014ba008 0000000000000000
raw: 00000000000005c2 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 6060, tgid 6060 (syz.2.19), ts 112783813754, free_ts 113851953043
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
prep_new_page mm/page_alloc.c:1854 [inline]
get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
folio_alloc_mpol_noprof+0x39/0xe0 mm/mempolicy.c:2505
shmem_alloc_folio mm/shmem.c:1890 [inline]
shmem_alloc_and_add_folio mm/shmem.c:1932 [inline]
shmem_get_folio_gfp+0x633/0x1a70 mm/shmem.c:2556
shmem_get_folio mm/shmem.c:2662 [inline]
shmem_write_begin+0x166/0x320 mm/shmem.c:3315
generic_perform_write+0x29d/0x8c0 mm/filemap.c:4314
shmem_file_write_iter+0xfb/0x120 mm/shmem.c:3490
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5d5/0xb40 fs/read_write.c:686
ksys_write+0x14b/0x260 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5931 tgid 5931 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
folios_put_refs+0x569/0x670 mm/swap.c:1002
folio_batch_release include/linux/pagevec.h:101 [inline]
shmem_undo_range+0x49e/0x1490 mm/shmem.c:1137
shmem_truncate_range mm/shmem.c:1249 [inline]
shmem_evict_inode+0x26e/0xa70 mm/shmem.c:1379
evict+0x5f4/0xae0 fs/inode.c:837
__dentry_kill+0x209/0x660 fs/dcache.c:670
finish_dput+0xc9/0x480 fs/dcache.c:879
__fput+0x69d/0xa80 fs/file_table.c:476
task_work_run+0x1d4/0x260 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0xff/0x4f0 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x2e3/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888052e81680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888052e81700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888052e81780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff888052e81800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888052e81880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
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If the report is already addressed, let syzbot know by replying with:
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[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] ocfs2: fix use-after-free when reading a bad inode
Author: karti...@gmail.com

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

When ocfs2_read_locked_inode() fails with -ENOMEM or other errors,
it calls make_bad_inode() to mark the inode as bad but still returns
a valid inode pointer through the iget machinery. The function
_ocfs2_get_system_file_inode() only checks for IS_ERR(inode) but
not for bad inodes, causing the bad inode to be returned to callers.

During orphan recovery, ocfs2_queue_orphans() gets this bad inode
for the orphan directory and passes it to ocfs2_dir_foreach().
Since the inode was never properly initialized due to the earlier
read failure, iterating the directory accesses freed or uninitialized
memory, triggering a use-after-free in ocfs2_check_dir_entry().

Fix this by adding an is_bad_inode() check in _ocfs2_get_system_file_inode()
after ocfs2_iget() returns. If the inode is bad, release it with iput()
and return NULL. This protects all callers of ocfs2_get_system_file_inode()
from receiving bad inodes.

Reported-by: syzbot+c89782...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---
fs/ocfs2/sysfile.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/ocfs2/sysfile.c b/fs/ocfs2/sysfile.c
index d53a6cc866be..f443479f7d3e 100644
--- a/fs/ocfs2/sysfile.c
+++ b/fs/ocfs2/sysfile.c
@@ -145,6 +145,13 @@ static struct inode * _ocfs2_get_system_file_inode(struct ocfs2_super *osb,
inode = NULL;
goto bail;
}
+
+ if(is_bad_inode(inode)) {
+ iput(inode);
+ inode = NULL;
+ goto bail;
+ }
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
if (type == LOCAL_USER_QUOTA_SYSTEM_INODE ||
type == LOCAL_GROUP_QUOTA_SYSTEM_INODE ||
--
2.43.0

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in ocfs2_check_dir_entry

(kworker/u8:17,5105,0):ocfs2_read_blocks_sync:112 ERROR: status = -12
(kworker/u8:17,5105,0):ocfs2_read_locked_inode:599 ERROR: status = -12

==================================================================
BUG: KASAN: use-after-free in ocfs2_check_dir_entry+0x3a0/0x480 fs/ocfs2/dir.c:318

Read of size 2 at addr ffff88805fe76780 by task kworker/u8:17/5105

CPU: 0 UID: 0 PID: 5105 Comm: kworker/u8:17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: ocfs2_wq ocfs2_complete_recovery
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_check_dir_entry+0x3a0/0x480 fs/ocfs2/dir.c:318
ocfs2_dir_foreach_blk_id fs/ocfs2/dir.c:1826 [inline]
ocfs2_dir_foreach_blk+0xfff/0x1420 fs/ocfs2/dir.c:1954
ocfs2_dir_foreach+0x42/0x70 fs/ocfs2/dir.c:1965
ocfs2_queue_orphans fs/ocfs2/journal.c:2215 [inline]
ocfs2_recover_orphans fs/ocfs2/journal.c:2299 [inline]
ocfs2_complete_recovery+0xc37/0x20b0 fs/ocfs2/journal.c:1366
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>

The buggy address belongs to the physical page:

page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1d1 pfn:0x5fe76
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea00017f93c8 ffffea00017f9ec8 0000000000000000
raw: 00000000000001d1 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 6496, tgid 6496 (cmp), ts 169634784819, free_ts 169719162751

set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
prep_new_page mm/page_alloc.c:1854 [inline]
get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486

folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
folio_prealloc+0x30/0x180 mm/memory.c:-1
do_cow_fault mm/memory.c:5779 [inline]
do_fault mm/memory.c:5891 [inline]
do_pte_missing+0x509/0x27a0 mm/memory.c:4401
handle_pte_fault mm/memory.c:6273 [inline]
__handle_mm_fault mm/memory.c:6411 [inline]
handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
page last free pid 6496 tgid 6496 stack trace:

reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
folios_put_refs+0x569/0x670 mm/swap.c:1002

free_pages_and_swap_cache+0x277/0x520 mm/swap_state.c:355
__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
exit_mmap+0x439/0xb10 mm/mmap.c:1290
__mmput+0xcb/0x3d0 kernel/fork.c:1173
exit_mm+0x1da/0x2c0 kernel/exit.c:581
do_exit+0x658/0x2310 kernel/exit.c:959
do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
__do_sys_exit_group kernel/exit.c:1123 [inline]
__se_sys_exit_group kernel/exit.c:1121 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
__pfx_syscall_get_nr+0x0/0x10 arch/x86/include/generated/asm/syscalls_64.h:232

do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:

ffff88805fe76680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805fe76700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805fe76780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88805fe76800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805fe76880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


Tested on:

commit: d358e525 Merge tag 'for-6.19/dm-changes' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138ef992580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f315601b98a91c0b

dashboard link: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
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=123891c2580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] ocfs2: validate inline directory i_size during inode read

Author: karti...@gmail.com

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

When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline
directories. If the filesystem is corrupted, an inline directory's
i_size can exceed the actual inline data capacity (id_count).

This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline
data buffer, triggering a use-after-free when accessing directory
entries from freed memory.

In the syzbot report:
- i_size was 1099511627576 bytes (~1TB)
- Actual inline data capacity (id_count) is typically <256 bytes
- A garbage rec_len (54648) caused ctx->pos to jump out of bounds
- This triggered a UAF in ocfs2_check_dir_entry()

Fix by adding a validation check in ocfs2_validate_inode_block() to
ensure inline directories have i_size <= id_count. This catches the
corruption early during inode read and prevents all downstream code
from operating on invalid data.

Reported-by: syzbot+c89782...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---

fs/ocfs2/inode.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 8340525e5589..9eb364bef5c3 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1521,6 +1521,21 @@ int ocfs2_validate_inode_block(struct super_block *sb,
}
}

+ if (S_ISDIR(le16_to_cpu(di->i_mode)) &&
+ (di->i_dyn_features & cpu_to_le16(OCFS2_INLINE_DATA_FL))) {
+ struct ocfs2_inline_data *data = &di->id2.i_data;
+
+ if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
+ rc = ocfs2_error(sb,
+ "Invalid dinode #%llu: inline directory "
+ "i_size %llu exceeds id_count %u\n",
+ (unsigned long long)bh->b_blocknr,
+ (unsigned long long)le64_to_cpu(di->i_size),
+ le16_to_cpu(data->id_count));

+ goto bail;
+ }
+ }

+
rc = 0;

bail:
--
2.43.0

[syzbot]

Hello,

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

Reported-by: syzbot+c89782...@syzkaller.appspotmail.com
Tested-by: syzbot+c89782...@syzkaller.appspotmail.com

Tested on:

commit: d358e525 Merge tag 'for-6.19/dm-changes' of git://git...
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=115bc61a580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f315601b98a91c0b
dashboard link: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
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=11b1f992580000

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