[syzbot] [netfs?] kernel BUG in netfs_perform_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b9a10f876409 Merge tag 'soc-fixes-6.17-2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148b6312580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d4703ac89d9e185a
dashboard link: https://syzkaller.appspot.com/bug?extid=b73c7d94a151e2ee1e9b
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14dd1a42580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12eb0134580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f78fc7403c46/disk-b9a10f87.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a6cdb7126dd0/vmlinux-b9a10f87.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3e315b6f116e/bzImage-b9a10f87.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b73c7d...@syzkaller.appspotmail.com

kill_anon_super+0x3a/0x60 fs/super.c:1282
v9fs_kill_super+0x3d/0xa0 fs/9p/vfs_super.c:195
deactivate_locked_super+0xc1/0x1a0 fs/super.c:474
deactivate_super fs/super.c:507 [inline]
deactivate_super+0xde/0x100 fs/super.c:503
cleanup_mnt+0x225/0x450 fs/namespace.c:1375
------------[ cut here ]------------
kernel BUG at mm/filemap.c:1498!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 6039 Comm: syz.0.22 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:folio_unlock mm/filemap.c:1498 [inline]
RIP: 0010:folio_unlock+0xb3/0xd0 mm/filemap.c:1493
Code: b3 5c c9 ff 48 89 ef 31 f6 e8 f9 ed ff ff 5b 5d e9 a2 5c c9 ff e8 9d 5c c9 ff 48 c7 c6 60 19 b9 8b 48 89 ef e8 0e 0d 12 00 90 <0f> 0b 48 89 df e8 d3 bb 2f 00 e9 7b ff ff ff 66 66 2e 0f 1f 84 00
RSP: 0018:ffffc90002e97980 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802f3cc880 RSI: ffffffff81f231a2 RDI: ffff88802f3cccc4
RBP: ffffea0001850e80 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90ab5c97 R11: 0000000000000000 R12: ffff88805caf0f00
R13: ffffc90002e97de8 R14: ffffea0001850e80 R15: dffffc0000000000
FS: 000055555d2d5500(0000) GS:ffff8881246b8000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c0071b4000 CR3: 000000007d73b000 CR4: 00000000003526f0
Call Trace:
<TASK>
netfs_perform_write+0xacd/0x1e60 fs/netfs/buffered_write.c:407
netfs_buffered_write_iter_locked fs/netfs/buffered_write.c:452 [inline]
netfs_file_write_iter+0x495/0x570 fs/netfs/buffered_write.c:491
v9fs_file_write_iter+0x9b/0x100 fs/9p/vfs_file.c:407
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x7d3/0x11d0 fs/read_write.c:686
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1f5f98ebe9
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:00007ffd97e08798 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1f5fbc5fa0 RCX: 00007f1f5f98ebe9
RDX: 0000000000000018 RSI: 0000200000000380 RDI: 0000000000000007
RBP: 00007f1f5fa11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1f5fbc5fa0 R14: 00007f1f5fbc5fa0 R15: 0000000000000003
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:folio_unlock mm/filemap.c:1498 [inline]
RIP: 0010:folio_unlock+0xb3/0xd0 mm/filemap.c:1493
Code: b3 5c c9 ff 48 89 ef 31 f6 e8 f9 ed ff ff 5b 5d e9 a2 5c c9 ff e8 9d 5c c9 ff 48 c7 c6 60 19 b9 8b 48 89 ef e8 0e 0d 12 00 90 <0f> 0b 48 89 df e8 d3 bb 2f 00 e9 7b ff ff ff 66 66 2e 0f 1f 84 00
RSP: 0018:ffffc90002e97980 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802f3cc880 RSI: ffffffff81f231a2 RDI: ffff88802f3cccc4
RBP: ffffea0001850e80 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90ab5c97 R11: 0000000000000000 R12: ffff88805caf0f00
R13: ffffc90002e97de8 R14: ffffea0001850e80 R15: dffffc0000000000
FS: 000055555d2d5500(0000) GS:ffff8881246b8000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c0071b4000 CR3: 000000007d73b000 CR4: 00000000003526f0


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Lizhi Xu]

#syz test

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index f27ea5099a68..09394ac2c180 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -347,7 +347,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
folio_put(folio);
ret = filemap_write_and_wait_range(mapping, fpos, fpos + flen - 1);
if (ret < 0)
- goto error_folio_unlock;
+ goto out;
continue;

copied:

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in v9fs_evict_inode

INFO: task syz-executor:10275 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:23976 pid:10275 tgid:10275 ppid:1 task_flags:0x400140 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5357 [inline]
__schedule+0x1190/0x5de0 kernel/sched/core.c:6961
__schedule_loop kernel/sched/core.c:7043 [inline]
schedule+0xe7/0x3a0 kernel/sched/core.c:7058
netfs_wait_for_outstanding_io include/linux/netfs.h:552 [inline]
v9fs_evict_inode+0x26f/0x300 fs/9p/vfs_inode.c:348
evict+0x3e3/0x920 fs/inode.c:810
iput_final fs/inode.c:1897 [inline]
iput fs/inode.c:1923 [inline]
iput+0x521/0x880 fs/inode.c:1909
dentry_unlink_inode+0x29c/0x480 fs/dcache.c:466
__dentry_kill+0x1d0/0x600 fs/dcache.c:669
dput.part.0+0x4b1/0x9b0 fs/dcache.c:911
dput fs/dcache.c:901 [inline]
do_one_tree fs/dcache.c:1607 [inline]
shrink_dcache_for_umount+0x159/0x3e0 fs/dcache.c:1621
generic_shutdown_super+0x6c/0x390 fs/super.c:621

kill_anon_super+0x3a/0x60 fs/super.c:1282
v9fs_kill_super+0x3d/0xa0 fs/9p/vfs_super.c:195
deactivate_locked_super+0xc1/0x1a0 fs/super.c:474
deactivate_super fs/super.c:507 [inline]
deactivate_super+0xde/0x100 fs/super.c:503
cleanup_mnt+0x225/0x450 fs/namespace.c:1375

task_work_run+0x150/0x240 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcecc38ff17
RSP: 002b:00007ffd3a66f178 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fcecc411c05 RCX: 00007fcecc38ff17
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd3a66f230
RBP: 00007ffd3a66f230 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffd3a6702c0
R13: 00007fcecc411c05 R14: 000000000003f589 R15: 00007ffd3a670300
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
#0: ffffffff8e5c1260 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8e5c1260 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#0: ffffffff8e5c1260 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
2 locks held by kworker/u8:3/37:
#0: ffff88801b881148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3211
#1: ffffc90000ad7d10 ((work_completion)(&rreq->cleanup_work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3212
2 locks held by getty/5606:
#0: ffff88814d69e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc900036bb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
1 lock held by syz-executor/10275:
#0: ffff88805bc120e0 (&type->s_umount_key#68){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
#0: ffff88805bc120e0 (&type->s_umount_key#68){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
#0: ffff88805bc120e0 (&type->s_umount_key#68){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
#0: ffff88805bc120e0 (&type->s_umount_key#68){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
1 lock held by syz-executor/14777:
#0: ffffffff8e5cc6c0 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x48/0x6e0 kernel/rcu/tree.c:3815

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025

Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:328 [inline]
watchdog+0xf0e/0x1260 kernel/hung_task.c:491
kthread+0x3c2/0x780 kernel/kthread.c:463
ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted syzkaller #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025

Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:__bfs+0x1ba/0x290 kernel/locking/lockdep.c:1815
Code: 01 15 44 29 cb 81 e3 ff 0f 00 00 39 1d df f5 45 14 48 89 04 f5 00 6a 98 96 73 0c 89 1d cf f5 45 14 eb 04 4c 89 78 30 48 8b 00 <4c> 39 c0 75 f4 e9 2b ff ff ff b8 01 00 00 00 48 83 c4 28 5b 5d 41
RSP: 0018:ffffc90000117300 EFLAGS: 00000006
RAX: ffffffff9770e2a8 RBX: 0000000000000001 RCX: 0000000000000001
RDX: 0000000000000111 RSI: 0000000000000001 RDI: ffffc900001173c0
RBP: 0000000000000030 R08: ffffffff95dd9b90 R09: 0000000000000001
R10: ffffc900001174a0 R11: 0000000000000000 R12: ffffffff81974ec0
R13: ffffc900001173a0 R14: ffffffff819759d0 R15: ffffc900001173c0
FS: 0000000000000000(0000) GS:ffff8881246b6000(0000) knlGS:0000000000000000

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

CR2: 0000555593ff75c8 CR3: 000000000e380000 CR4: 00000000003526f0
Call Trace:
<TASK>
__bfs_backwards kernel/locking/lockdep.c:1860 [inline]
check_irq_usage+0xcb/0x920 kernel/locking/lockdep.c:2796
check_prev_add kernel/locking/lockdep.c:3169 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x12bc/0x1ce0 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
lock_hrtimer_base kernel/time/hrtimer.c:171 [inline]
hrtimer_try_to_cancel+0xa9/0x2f0 kernel/time/hrtimer.c:1362
update_curr_dl_se+0x42c/0xa10 kernel/sched/deadline.c:1468
update_curr+0x3fb/0x550 kernel/sched/fair.c:1243
pick_task_fair+0x171/0x330 kernel/sched/fair.c:8753
pick_next_task_fair+0x20/0x1010 kernel/sched/fair.c:8778
__pick_next_task+0xf1/0x6c0 kernel/sched/core.c:6001
pick_next_task kernel/sched/core.c:6099 [inline]
__schedule+0x5d3/0x5de0 kernel/sched/core.c:6902
preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:7145
preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
on_each_cpu_cond_mask+0x75/0x90 kernel/smp.c:1045
on_each_cpu include/linux/smp.h:71 [inline]
smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2653 [inline]
smp_text_poke_batch_finish+0x7b4/0xdb0 arch/x86/kernel/alternative.c:2946
arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
jump_label_update+0x376/0x550 kernel/jump_label.c:919
static_key_enable_cpuslocked+0x1b7/0x270 kernel/jump_label.c:210
static_key_enable+0x1a/0x20 kernel/jump_label.c:223
toggle_allocation_gate mm/kfence/core.c:850 [inline]
toggle_allocation_gate+0xfa/0x280 mm/kfence/core.c:842
process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3236
process_scheduled_works kernel/workqueue.c:3319 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
kthread+0x3c2/0x780 kernel/kthread.c:463
ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


Tested on:

commit: d69eb204 Merge tag 'net-6.17-rc5' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1551b162580000

kernel config: https://syzkaller.appspot.com/x/.config?x=d4703ac89d9e185a
dashboard link: https://syzkaller.appspot.com/bug?extid=b73c7d94a151e2ee1e9b
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13dd1312580000

[Lizhi Xu]

The filio lock has been released here, so there is no need to jump to
error_folio_unlock to release it again.

Reported-by: syzbot+b73c7d...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b73c7d94a151e2ee1e9b
Signed-off-by: Lizhi Xu <lizh...@windriver.com>
---
fs/netfs/buffered_write.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--
2.43.0