[syzbot] [xfs?] INFO: task hung in xfs_inodegc_flush

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 076d56d74f17 Add linux-next specific files for 20240202
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=173b568fe80000
kernel config: https://syzkaller.appspot.com/x/.config?x=428086ff1c010d9f
dashboard link: https://syzkaller.appspot.com/bug?extid=0260338e3eff65854d1f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148b3c9fe80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13811004180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dece45d1a4b5/disk-076d56d7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4921e269b178/vmlinux-076d56d7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2a9156da9091/bzImage-076d56d7.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9938609b8cc3/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+026033...@syzkaller.appspotmail.com

INFO: task syz-executor218:5106 blocked for more than 143 seconds.
Not tainted 6.8.0-rc2-next-20240202-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor218 state:D stack:18928 pid:5106 tgid:5106 ppid:5102 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5400 [inline]
__schedule+0x17df/0x4a40 kernel/sched/core.c:6727
__schedule_loop kernel/sched/core.c:6804 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6819
schedule_timeout+0xb0/0x310 kernel/time/timer.c:2159
do_wait_for_common kernel/sched/completion.c:95 [inline]
__wait_for_common kernel/sched/completion.c:116 [inline]
wait_for_common kernel/sched/completion.c:127 [inline]
wait_for_completion+0x355/0x620 kernel/sched/completion.c:148
__flush_workqueue+0x730/0x1630 kernel/workqueue.c:3617
xfs_inodegc_wait_all fs/xfs/xfs_icache.c:465 [inline]
xfs_inodegc_flush+0xe1/0x3e0 fs/xfs/xfs_icache.c:1912
xfs_unmountfs+0x25/0x200 fs/xfs/xfs_mount.c:1064
xfs_fs_put_super+0x65/0x140 fs/xfs/xfs_super.c:1136
generic_shutdown_super+0x136/0x2d0 fs/super.c:646
kill_block_super+0x44/0x90 fs/super.c:1680
xfs_kill_sb+0x15/0x50 fs/xfs/xfs_super.c:2026
deactivate_locked_super+0xc4/0x130 fs/super.c:477
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:108 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:212
do_syscall_64+0x10a/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f1a396ed8f7
RSP: 002b:00007ffec055f888 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f1a396ed8f7
RDX: 0000000000000000 RSI: 000000000000000a RDI: 00007ffec055f940
RBP: 00007ffec055f940 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000206 R12: 00007ffec05609b0
R13: 000055555739d6c0 R14: 00000000000c93c9 R15: 0000000000000108
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8e130d60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
#0: ffffffff8e130d60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
#0: ffffffff8e130d60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
2 locks held by getty/4817:
#0: ffff88802a9230a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc90002f162f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2201
1 lock held by syz-executor218/5106:
#0: ffff88807f4d40e0 (&type->s_umount_key#48){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
#0: ffff88807f4d40e0 (&type->s_umount_key#48){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
#0: ffff88807f4d40e0 (&type->s_umount_key#48){+.+.}-{3:3}, at: deactivate_super+0xb5/0xf0 fs/super.c:509

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted 6.8.0-rc2-next-20240202-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xfb0/0xff0 kernel/hung_task.c:379
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:242
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt+0x21/0x30 drivers/acpi/processor_idle.c:112


---
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[Hillf Danton]

On Wed, 07 Feb 2024 00:44:21 -0800

> HEAD commit: 076d56d74f17 Add linux-next specific files for 20240202
> git tree: linux-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13811004180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 076d56d74f17

--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1999,6 +1999,8 @@ static int try_to_grab_pending(struct wo
*/
pwq = get_work_pwq(work);
if (pwq && pwq->pool == pool) {
+ unsigned long work_data;
+
debug_work_deactivate(work);

/*
@@ -2016,11 +2018,12 @@ static int try_to_grab_pending(struct wo

list_del_init(&work->entry);

+ work_data = *work_data_bits(work);
/* work->data points to pwq iff queued, point to pool */
set_work_pool_and_keep_pending(work, pool->id);

/* must be the last step, see the function comment */
- pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
+ pwq_dec_nr_in_flight(pwq, work_data);

raw_spin_unlock(&pool->lock);
rcu_read_unlock();
--

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to checkout kernel repo https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git on commit 076d56d74f17: failed to run ["git" "fetch" "--force" "--tags" "fc608f7504e8b3e110eb6e7b798cef357818c5e1" "076d56d74f17"]: exit status 128
fatal: couldn't find remote ref 076d56d74f17



Tested on:

commit: [unknown
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 076d56d74f17

kernel config: https://syzkaller.appspot.com/x/.config?x=428086ff1c010d9f
dashboard link: https://syzkaller.appspot.com/bug?extid=0260338e3eff65854d1f
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=14b53360180000

[Dave Chinner]

On Wed, Feb 07, 2024 at 12:44:21AM -0800, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 076d56d74f17 Add linux-next specific files for 20240202
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=173b568fe80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=428086ff1c010d9f
> dashboard link: https://syzkaller.appspot.com/bug?extid=0260338e3eff65854d1f
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148b3c9fe80000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13811004180000

.....

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

#syz fix: workqueue: Fix pwq->nr_in_flight corruption in try_to_grab_pending()


--
Dave Chinner
da...@fromorbit.com