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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cea2a26553ac mailmap: Add my outdated addresses to the map..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=118b1796980000
kernel config: https://syzkaller.appspot.com/x/.config?x=b8786f381e62940f
dashboard link: https://syzkaller.appspot.com/bug?extid=c0831b61d6ade1e2d098
compiler: gcc (Debian 12.2.0-14) 12.2.0, 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/c2c55a2edceb/disk-cea2a265.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e3f36f58a11d/vmlinux-cea2a265.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0447e9647456/bzImage-cea2a265.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c0831b...@syzkaller.appspotmail.com

INFO: task syz-executor.2:20070 blocked for more than 143 seconds.
Not tainted 6.10.0-rc3-syzkaller-00022-gcea2a26553ac #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.2 state:D stack:27840 pid:20070 tgid:20068 ppid:19010 flags:0x00000006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5408 [inline]
__schedule+0xf15/0x5d00 kernel/sched/core.c:6745
__schedule_loop kernel/sched/core.c:6822 [inline]
schedule+0xe7/0x350 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+0x5b8/0x9c0 kernel/locking/mutex.c:752
nfsd_nl_threads_get_doit+0x1c6/0x7d0 fs/nfsd/nfsctl.c:1757
genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x16b/0x440 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+0x542/0x820 net/netlink/af_netlink.c:1361
netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1905
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0xab5/0xc90 net/socket.c:2585
___sys_sendmsg+0x135/0x1e0 net/socket.c:2639
__sys_sendmsg+0x117/0x1f0 net/socket.c:2668
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8368c7cea9
RSP: 002b:00007f8369a710c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f8368db3f80 RCX: 00007f8368c7cea9
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 00007f8368cebff4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f8368db3f80 R15: 00007ffc121dd2e8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
#0: ffffffff8dbb1920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#0: ffffffff8dbb1920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#0: ffffffff8dbb1920 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x75/0x340 kernel/locking/lockdep.c:6614
2 locks held by getty/4834:
#0: ffff88802a5540a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xfc8/0x1490 drivers/tty/n_tty.c:2201
1 lock held by syz-fuzzer/5075:
3 locks held by kworker/0:4/10299:
#0: ffff888015480948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12bf/0x1b60 kernel/workqueue.c:3206
#1: ffffc900032cfd80 (free_ipc_work){+.+.}-{0:0}, at: process_one_work+0x957/0x1b60 kernel/workqueue.c:3207
#2: ffffffff8dbbd0b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock+0x282/0x3b0 kernel/rcu/tree_exp.h:291
2 locks held by syz-executor.0/19218:
#0: ffffffff8f7e9d90 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
#1: ffffffff8dfb2f48 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_listener_set_doit+0xe3/0x1b30 fs/nfsd/nfsctl.c:1966
1 lock held by syz-executor.1/19451:
3 locks held by kworker/u8:0/20032:
2 locks held by syz-executor.2/20070:
#0: ffffffff8f7e9d90 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
#1: ffffffff8dfb2f48 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_threads_get_doit+0x1c6/0x7d0 fs/nfsd/nfsctl.c:1757
3 locks held by syz-executor.4/20215:
#0: ffff8880560b0d88 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:554
#1: ffff8880560b0078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x339/0x1100 net/bluetooth/hci_sync.c:5050
#2: ffffffff8f9adba8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1982 [inline]
#2: ffffffff8f9adba8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xc4/0x260 net/bluetooth/hci_conn.c:2584
2 locks held by syz-executor.2/20315:
3 locks held by syz-executor.3/20448:
#0: ffff888063cf4d88 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:554
#1: ffff888063cf4078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x339/0x1100 net/bluetooth/hci_sync.c:5050
#2: ffffffff8f9adba8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1982 [inline]
#2: ffffffff8f9adba8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xc4/0x260 net/bluetooth/hci_conn.c:2584
1 lock held by syz-executor.0/21407:
#0: ffffffff8dbbd0b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock+0x1a4/0x3b0 kernel/rcu/tree_exp.h:323

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

NMI backtrace for cpu 0
CPU: 0 PID: 30 Comm: khungtaskd Not tainted 6.10.0-rc3-syzkaller-00022-gcea2a26553ac #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+0x116/0x1f0 lib/dump_stack.c:114
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:162 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
watchdog+0xf86/0x1240 kernel/hung_task.c:379
kthread+0x2c1/0x3a0 kernel/kthread.c:389
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt+0x1a/0x20 drivers/acpi/processor_idle.c:112


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