[syzbot] [nfs?] INFO: task hung in nfsd_nl_version_get_doit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2ccbdf43d5e7 Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17a8c3de980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c79815c08cc14227
dashboard link: https://syzkaller.appspot.com/bug?extid=41bc60511c2884783c27
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9fb20954c51e/disk-2ccbdf43.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/06d78b3cf960/vmlinux-2ccbdf43.xz
kernel image: https://storage.googleapis.com/syzbot-assets/15e5b0a8df77/bzImage-2ccbdf43.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+41bc60...@syzkaller.appspotmail.com

INFO: task syz-executor.2:26515 blocked for more than 144 seconds.
Not tainted 6.10.0-rc3-syzkaller-00044-g2ccbdf43d5e7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.2 state:D stack:26328 pid:26515 tgid:26509 ppid:26207 flags:0x00000006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5408 [inline]
__schedule+0x1796/0x49d0 kernel/sched/core.c:6745
__schedule_loop kernel/sched/core.c:6822 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6837
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6894
__mutex_lock_common kernel/locking/mutex.c:684 [inline]
__mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752
nfsd_nl_version_get_doit+0x181/0x780 fs/nfsd/nfsctl.c:1892
genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0xb14/0xec0 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2564
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1361
netlink_sendmsg+0x8db/0xcb0 net/netlink/af_netlink.c:1905
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x221/0x270 net/socket.c:745
____sys_sendmsg+0x525/0x7d0 net/socket.c:2585
___sys_sendmsg net/socket.c:2639 [inline]
__sys_sendmsg+0x2b0/0x3a0 net/socket.c:2668
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7e21a7cea9
RSP: 002b:00007f7e228320c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7e21bb4120 RCX: 00007f7e21a7cea9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 000000000000000c
RBP: 00007f7e21aebff4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f7e21bb4120 R15: 00007ffcc0bd6078
</TASK>

Showing all locks held in the system:
1 lock held by pool_workqueue_/3:
1 lock held by khungtaskd/30:
#0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
2 locks held by kworker/u8:6/1098:
2 locks held by getty/4840:
#0: ffff88802abac0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc90002f0e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2201
2 locks held by syz-fuzzer/5091:
3 locks held by kworker/0:0/15508:
#0: ffff888015080948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3206 [inline]
#0: ffff888015080948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x90a/0x1830 kernel/workqueue.c:3312
#1: ffffc9000429fd00 (free_ipc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3207 [inline]
#1: ffffc9000429fd00 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0x945/0x1830 kernel/workqueue.c:3312
#2: ffffffff8e339378 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
#2: ffffffff8e339378 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x451/0x830 kernel/rcu/tree_exp.h:939
2 locks held by kworker/u8:14/18935:
2 locks held by syz-executor.0/25819:
#0: ffffffff8f63b9d0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
#1: ffffffff8e600748 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_listener_set_doit+0x12d/0x1a90 fs/nfsd/nfsctl.c:1966
2 locks held by syz-executor.2/26515:
#0: ffffffff8f63b9d0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
#1: ffffffff8e600748 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_version_get_doit+0x181/0x780 fs/nfsd/nfsctl.c:1892
2 locks held by syz-executor.3/26579:
#0: ffffffff8f63b9d0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
#1: ffffffff8e600748 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_version_get_doit+0x181/0x780 fs/nfsd/nfsctl.c:1892
1 lock held by syz-executor.2/28062:
#0: ffffffff8e339378 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#0: ffffffff8e339378 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x381/0x830 kernel/rcu/tree_exp.h:939
1 lock held by syz-executor.3/28067:

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

NMI backtrace for cpu 1
CPU: 1 PID: 30 Comm: khungtaskd Not tainted 6.10.0-rc3-syzkaller-00044-g2ccbdf43d5e7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
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:162 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
watchdog+0xfde/0x1020 kernel/hung_task.c:379
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 28056 Comm: syz-executor.0 Not tainted 6.10.0-rc3-syzkaller


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