[v6.1] INFO: task hung in vfs_unlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ca48fc16c493 Linux 6.1.27
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17dca3f4280000
kernel config: https://syzkaller.appspot.com/x/.config?x=47d3bbfdb3b1ddd2
dashboard link: https://syzkaller.appspot.com/bug?extid=a8267ca8983a737a4570
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/658765c915fa/disk-ca48fc16.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d69e8a1aff2d/vmlinux-ca48fc16.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0317a9546209/bzImage-ca48fc16.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a8267c...@syzkaller.appspotmail.com

INFO: task syz-fuzzer:3702 blocked for more than 143 seconds.
Not tainted 6.1.27-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-fuzzer state:D stack:22152 pid:3702 ppid:3538 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5241 [inline]
__schedule+0x132c/0x4330 kernel/sched/core.c:6554
schedule+0xbf/0x180 kernel/sched/core.c:6630
rwsem_down_write_slowpath+0xe93/0x14a0 kernel/locking/rwsem.c:1189
inode_lock include/linux/fs.h:756 [inline]
vfs_unlink+0xe0/0x5f0 fs/namei.c:4241
do_unlinkat+0x49d/0x940 fs/namei.c:4320
__do_sys_unlinkat fs/namei.c:4363 [inline]
__se_sys_unlinkat fs/namei.c:4356 [inline]
__x64_sys_unlinkat+0xca/0xf0 fs/namei.c:4356
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x403ace
RSP: 002b:000000c000ba14b8 EFLAGS: 00000206 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 0000000000403ace
RDX: 0000000000000000 RSI: 000000c023780030 RDI: 0000000000000016
RBP: 000000c000ba14f8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000003 R14: 000000c0118ac000 R15: 000000c024e74800
</TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cf273f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xd20 kernel/rcu/tasks.h:510
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cf27bf0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xd20 kernel/rcu/tasks.h:510
1 lock held by khungtaskd/28:
#0: ffffffff8cf27220 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
1 lock held by syslogd/2982:
2 locks held by getty/3306:
#0: ffff888029861098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc900031262f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a7/0x1db0 drivers/tty/n_tty.c:2177
3 locks held by syz-fuzzer/3702:
#0: ffff88807ef6a460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393
#1: ffff888088db5e48 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:791 [inline]
#1: ffff888088db5e48 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: do_unlinkat+0x260/0x940 fs/namei.c:4303
#2: ffff88808758f258 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
#2: ffff88808758f258 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: vfs_unlink+0xe0/0x5f0 fs/namei.c:4241
2 locks held by kworker/u4:13/4102:
3 locks held by syz-executor.1/10604:

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.1.27-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
nmi_cpu_backtrace+0x4e1/0x560 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b0/0x3f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xf18/0xf60 kernel/hung_task.c:377
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3612 Comm: kworker/u4:3 Not tainted 6.1.27-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
RIP: 0010:check_preemption_disabled+0x5c/0x110 lib/smp_processor_id.c:19
Code: 25 28 00 00 00 48 3b 44 24 08 0f 85 c7 00 00 00 89 d8 48 83 c4 10 5b 41 5c 41 5e 41 5f c3 48 c7 04 24 00 00 00 00 9c 8f 04 24 <f7> 04 24 00 02 00 00 74 c9 49 89 f6 49 89 ff 65 4c 8b 25 bd dd 80
RSP: 0018:ffffc90003ebf8a8 EFLAGS: 00000046
RAX: 0000000080000000 RBX: 0000000000000000 RCX: 1ffff920007d7ec8
RDX: dffffc0000000000 RSI: ffffffff8aebe1a0 RDI: ffffffff8b3cbfa0
RBP: ffffc90003ebfa40 R08: dffffc0000000000 R09: fffffbfff2050445
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920007d7f24
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000246
FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c02452a8f0 CR3: 000000000cc8e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lockdep_recursion_finish kernel/locking/lockdep.c:467 [inline]
lock_acquire+0x208/0x5a0 kernel/locking/lockdep.c:5671
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:306
rcu_read_lock include/linux/rcupdate.h:747 [inline]
batadv_iv_ogm_slide_own_bcast_window net/batman-adv/bat_iv_ogm.c:755 [inline]
batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:826 [inline]
batadv_iv_ogm_schedule+0x425/0x1000 net/batman-adv/bat_iv_ogm.c:869
batadv_iv_send_outstanding_bat_ogm_packet+0x6fa/0x800 net/batman-adv/bat_iv_ogm.c:1713
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.