[syzbot ci] Re: ext4: deferred iput framework for EA inodes

[syzbot ci]

syzbot ci has tested the following series

[v9] ext4: deferred iput framework for EA inodes
https://lore.kernel.org/all/20260623083540.2...@windriver.com
* [PATCH v9 1/4] fs: add iput_if_not_last() helper
* [PATCH v9 2/4] ext4: introduce ext4_put_ea_inode() for safe deferred iput
* [PATCH v9 3/4] ext4: convert all EA inode iput() calls to ext4_put_ea_inode()
* [PATCH v9 4/4] ext4: remove ea_inode_array mechanism in favor of ext4_put_ea_inode()

and found the following issue:
WARNING: ODEBUG bug in flush_delayed_work

Full report is available here:
https://ci.syzbot.org/series/acc1a7bd-816f-451e-86ee-a62f88ad8fcc

***

WARNING: ODEBUG bug in flush_delayed_work

tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 502d801f0ab03e4f32f9a33d203154ce84887921
arch: amd64
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
config: https://ci.syzbot.org/builds/79d2cdf0-fde6-4e70-a88c-04d44c9d3e44/config
syz repro: https://ci.syzbot.org/findings/9b2e3f5d-279a-469f-9f2a-05f96ea11587/syz_repro

EXT4-fs warning (device loop2): ext4_multi_mount_protect:287: Invalid MMP block in superblock
------------[ cut here ]------------
ODEBUG: assert_init not available (active state 0) object: ffff8881bf08c9e0 object type: timer_list hint: 0x0
WARNING: lib/debugobjects.c:632 at debug_print_object+0xec/0x230 lib/debugobjects.c:629, CPU#1: syz.2.19/5833
Modules linked in:
CPU: 1 UID: 0 PID: 5833 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:debug_print_object+0x18a/0x230 lib/debugobjects.c:629
Code: f8 48 c1 e8 03 80 3c 18 00 74 08 4c 89 ff e8 5d 04 71 fd 4d 8b 0f 4c 89 ef 48 8b 74 24 08 48 89 ea 44 89 e1 4d 89 f0 ff 34 24 <67> 48 0f b9 3a 48 83 c4 08 ff 05 a3 23 70 0b 48 83 c4 10 5b 41 5c
RSP: 0018:ffffc9000179f848 EFLAGS: 00010046

RAX: 1ffffffff179eacc RBX: dffffc0000000000 RCX: 0000000000000000
RDX: ffffffff8c2a9980 RSI: ffffffff8c2a93e0 RDI: ffffffff903ddbf0
RBP: ffffffff8c2a9980 R08: ffff8881bf08c9e0 R09: ffffffff8bcf69c0
R10: dffffc0000000000 R11: ffffffff81b25990 R12: 0000000000000000
R13: ffffffff903ddbf0 R14: ffff8881bf08c9e0 R15: ffffffff8bcf5660
FS: 00007fd11e12e6c0(0000) GS:ffff8882a922d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe46d80f88 CR3: 00000001bf40e000 CR4: 00000000000006f0
Call Trace:
<TASK>
debug_object_assert_init+0x237/0x370 lib/debugobjects.c:1075
debug_timer_assert_init kernel/time/timer.c:803 [inline]
debug_assert_init kernel/time/timer.c:848 [inline]
__try_to_del_timer_sync kernel/time/timer.c:1457 [inline]
__timer_delete_sync+0x181/0x520 kernel/time/timer.c:1621
flush_delayed_work+0x48/0x100 kernel/workqueue.c:4414
ext4_drain_ea_inode_work fs/ext4/xattr.h:196 [inline]
__ext4_fill_super fs/ext4/super.c:5795 [inline]
ext4_fill_super+0x54c7/0x66d0 fs/ext4/super.c:5844
get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1634
vfs_get_tree+0x92/0x2a0 fs/super.c:1694
fc_mount fs/namespace.c:1198 [inline]
do_new_mount_fc fs/namespace.c:3765 [inline]
do_new_mount+0x319/0xdc0 fs/namespace.c:3841
do_mount fs/namespace.c:4174 [inline]
__do_sys_mount fs/namespace.c:4390 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4367
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd11d19e0ca
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fd11e12de58 EFLAGS: 00000246
ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fd11e12dee0 RCX: 00007fd11d19e0ca
RDX: 0000200000000400 RSI: 0000200000000340 RDI: 00007fd11e12dea0
RBP: 0000200000000400 R08: 00007fd11e12dee0 R09: 000000000021c91c
R10: 000000000021c91c R11: 0000000000000246 R12: 0000200000000340
R13: 00007fd11e12dea0 R14: 000000000000051a R15: 0000200000000240
</TASK>
----------------
Code disassembly (best guess):
0: f8 clc
1: 48 c1 e8 03 shr $0x3,%rax
5: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1)
9: 74 08 je 0x13
b: 4c 89 ff mov %r15,%rdi
e: e8 5d 04 71 fd call 0xfd710470
13: 4d 8b 0f mov (%r15),%r9
16: 4c 89 ef mov %r13,%rdi
19: 48 8b 74 24 08 mov 0x8(%rsp),%rsi
1e: 48 89 ea mov %rbp,%rdx
21: 44 89 e1 mov %r12d,%ecx
24: 4d 89 f0 mov %r14,%r8
27: ff 34 24 push (%rsp)
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 83 c4 08 add $0x8,%rsp
33: ff 05 a3 23 70 0b incl 0xb7023a3(%rip) # 0xb7023dc
39: 48 83 c4 10 add $0x10,%rsp
3d: 5b pop %rbx
3e: 41 5c pop %r12


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syz...@syzkaller.appspotmail.com

---
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[syzbot ci]

syzbot ci has tested the following series

[v13] ext4: deferred iput framework for EA inodes
https://lore.kernel.org/all/20260702152225.4...@windriver.com
* [PATCH v13 1/4] fs: add iput_if_not_last() helper
* [PATCH v13 2/4] ext4: introduce ext4_put_ea_inode() for safe deferred iput
* [PATCH v13 3/4] ext4: convert all EA inode iput() calls to ext4_put_ea_inode()
* [PATCH v13 4/4] ext4: remove ea_inode_array mechanism in favor of ext4_put_ea_inode()

and found the following issue:

WARNING in ext4_journal_check_start

Full report is available here:

https://ci.syzbot.org/series/ce304d7b-7f32-44b5-bf6f-e579abb42a5c

***

WARNING in ext4_journal_check_start

tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux

base: 4a50a141f05a8d1737661b19ee22ff8455b94409

arch: amd64
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6

config: https://ci.syzbot.org/builds/e5413370-cf09-4540-b9d3-7d280f314ae0/config
syz repro: https://ci.syzbot.org/findings/e7cd69b7-8bb9-4554-bd84-b5ebcd7a8089/syz_repro

------------[ cut here ]------------
sb_rdonly(sb)
WARNING: fs/ext4/ext4_jbd2.c:75 at ext4_journal_check_start+0x24f/0x2b0 fs/ext4/ext4_jbd2.c:75, CPU#0: kworker/0:5/5860
Modules linked in:
CPU: 0 UID: 0 PID: 5860 Comm: kworker/0:5 Not tainted syzkaller #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014

Workqueue: events ext4_ea_inode_work
RIP: 0010:ext4_journal_check_start+0x24f/0x2b0 fs/ext4/ext4_jbd2.c:75
Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 06 75 42 ff 41 bf fb ff ff ff eb e0 e8 f9 74 42 ff eb d3 e8 f2 74 42 ff 90 <0f> 0b 90 eb c8 e8 e7 74 42 ff 90 0f 0b 90 43 80 7c 25 00 00 0f 85
RSP: 0018:ffffc900036bf888 EFLAGS: 00010293
RAX: ffffffff8283ecce RBX: ffff888170078000 RCX: ffff888107390000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 00000000000000ef R08: ffff8881bb53440f R09: 1ffff110376a6881
R10: dffffc0000000000 R11: ffffed10376a6882 R12: dffffc0000000000
R13: 1ffff1102e00f0cd R14: ffff888170078668 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88818dc20000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000055557b325a28 CR3: 0000000114bfe000 CR4: 00000000000006f0
Call Trace:
<TASK>
__ext4_journal_start_sb+0x147/0x5d0 fs/ext4/ext4_jbd2.c:107
__ext4_journal_start fs/ext4/ext4_jbd2.h:242 [inline]
ext4_evict_inode+0x7cb/0xf70 fs/ext4/inode.c:238
evict+0x624/0xb50 fs/inode.c:825
ext4_ea_inode_work+0x5c/0x90 fs/ext4/xattr.c:2974
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

[Jan Kara]

On Thu 02-07-26 15:57:01, syzbot ci wrote:
> syzbot ci has tested the following series
>
> [v13] ext4: deferred iput framework for EA inodes
> https://lore.kernel.org/all/20260702152225.4...@windriver.com
> * [PATCH v13 1/4] fs: add iput_if_not_last() helper
> * [PATCH v13 2/4] ext4: introduce ext4_put_ea_inode() for safe deferred iput
> * [PATCH v13 3/4] ext4: convert all EA inode iput() calls to ext4_put_ea_inode()
> * [PATCH v13 4/4] ext4: remove ea_inode_array mechanism in favor of ext4_put_ea_inode()
>
> and found the following issue:
> WARNING in ext4_journal_check_start

Good catch. We need to flush the pending work with iputs also in
ext4_sync_fs() which should also take care of this race with remount
read-only (and the same issue with filesystem freezing etc.).

Honza

--
Jan Kara <ja...@suse.com>
SUSE Labs, CR

[Zhou, Yun]

Hi Jan,

On 7/3/26 22:02, Jan Kara wrote:
>
> On Thu 02-07-26 15:57:01, syzbot ci wrote:
>> syzbot ci has tested the following series
>>
>> [v13] ext4: deferred iput framework for EA inodes
>> https://lore.kernel.org/all/20260702152225.4...@windriver.com
>> * [PATCH v13 1/4] fs: add iput_if_not_last() helper
>> * [PATCH v13 2/4] ext4: introduce ext4_put_ea_inode() for safe deferred iput
>> * [PATCH v13 3/4] ext4: convert all EA inode iput() calls to ext4_put_ea_inode()
>> * [PATCH v13 4/4] ext4: remove ea_inode_array mechanism in favor of ext4_put_ea_inode()
>>
>> and found the following issue:
>> WARNING in ext4_journal_check_start
>
> Good catch. We need to flush the pending work with iputs also in
> ext4_sync_fs() which should also take care of this race with remount
> read-only (and the same issue with filesystem freezing etc.).
>

Sorry for the late reply—I missed it because I receive too many emails
from syzbot. I've now reconfigured my filtering rules.

Regarding the issue reported by syzbot CI, would it be better to add
flush_delayed_work in __ext4_remount before sb->s_flags |= SB_RDONLY?
That would make the race window smaller.

Also, should I resend the v14 series, or submit a separate patch
specifically for this fix?

BR,
Yun

[Jan Kara]

Hi Yun,

Well, if there is remount read-only happening, the operations modifying
filesystem are blocked or made to fail (see mnt_get_write_access() /
sb_prepare_remount_readonly()). So it doesn't really matter where in
ext4_reconfigure() / __ext4_remount() we flush the work - no new items that
are deleting any xattr inodes should be added.

And placing the flushing into ext4_sync_fs() handles multiple similar
problems - sync(2) should make sure all pending deletions are finished,
remount needs to do this (and it calls sync_filesystem() which will end up
calling ext4_sync_fs()), fsfreeze needs to do this (it calls
sync_filesystem() as well).

> Also, should I resend the v14 series, or submit a separate patch
> specifically for this fix?

I think you can resend with the fixup. Ted didn't merge the series yet.

Honza