INFO: task hung in write_ports

Status: upstream: reported on 2026/07/27 22:00
Reported-by: syzbot+09b22ae5137f6827fa80@syzkaller.appspotmail.com
First crash: 9d07h, last: 9d02h
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in write_ports nfs prio:low 1 syz, C error 38 2h43m 5d05h 0/29 upstream: reported C repro on 2026/08/01 00:01
linux-6.1 INFO: task hung in write_ports 1 3 2d07h 9d09h 0/3 upstream: reported on 2026/07/27 20:14
linux-6.6 INFO: task hung in write_ports 1 4 1d00h 8d16h 0/2 upstream: reported on 2026/07/28 12:50

Sample crash report:
INFO: task syz.1.2068:10077 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.2068      state:D stack:27888 pid:10077 ppid:  9696 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
 __mutex_lock_common+0xdf5/0x2400 kernel/locking/mutex.c:669
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:848
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x304/0xd70 fs/read_write.c:592
 ksys_write+0x153/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f146a3c8e99
RSP: 002b:00007f1468621028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f146a650fa0 RCX: 00007f146a3c8e99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f146a45eeaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f146a651038 R14: 00007f146a650fa0 R15: 00007ffded3292b8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3945:
 #0: ffff88814c52c098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x594/0x1a50 drivers/tty/n_tty.c:2158
2 locks held by kworker/1:9/4278:
 #0: ffff888016c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
 #1: ffffc900031bfd00 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
3 locks held by syz.4.1856/9387:
 #0: ffff88807d7aaaf0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88805d2f8460 (sb_writers#43){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
 #2: ffffffff8c571728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:848
3 locks held by syz.1.2068/10077:
 #0: ffff888022b85c70 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88805d35c460 (sb_writers#43){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
 #2: ffffffff8c571728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:848
3 locks held by syz.6.3628/14532:
 #0: ffff8880261145f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88804c7e4460 (sb_writers#43){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
 #2: ffffffff8c571728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd4_write_time+0xa4/0x330 fs/nfsd/nfsctl.c:982
4 locks held by syz.3.3650/14582:
 #0: ffff8880749e0e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #0: ffff8880749e0e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:650 [inline]
 #0: ffff8880749e0e10 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x82/0x210 net/socket.c:1346
 #1: ffffffff8d4a8510 ((netlink_chain).rwsem){++++}-{3:3}, at: blocking_notifier_call_chain+0x5e/0x1b0 kernel/notifier.c:317
 #2: ffff888063fadcb8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nft_rcv_nl_event+0x126/0x5c0 net/netfilter/nf_tables_api.c:10632
 #3: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
 #3: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3a5/0x750 kernel/rcu/tree_exp.h:845
2 locks held by dhcpcd/14589:
 #0: ffff888057bb1410 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #0: ffff888057bb1410 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:650 [inline]
 #0: ffff888057bb1410 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x82/0x210 net/socket.c:1346
 #1: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
 #1: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2d1/0x750 kernel/rcu/tree_exp.h:845
1 lock held by dhcpcd/14590:
 #0: ffff8880292a6120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline]
 #0: ffff8880292a6120 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xd60 net/packet/af_packet.c:3218

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
 watchdog+0xe1b/0xe60 kernel/hung_task.c:369
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 154 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:hlist_del include/linux/list.h:871 [inline]
RIP: 0010:__alloc_object lib/debugobjects.c:217 [inline]
RIP: 0010:alloc_object+0x12d/0x640 lib/debugobjects.c:230
Code: e4 74 27 49 83 c4 08 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 e7 e8 77 3c d1 fd 49 89 1c 24 <48> b8 00 00 00 00 00 fc ff df 41 80 3c 06 00 49 89 ec 74 08 4c 89
RSP: 0018:ffffc90001f97220 EFLAGS: 00000046
RAX: 1ffff1100bfa6616 RBX: ffff8880b9137010 RCX: dffffc0000000000
RDX: ffffffff8a2c3120 RSI: ffffffff8a7a41e0 RDI: ffffffff8a7a41a0
RBP: ffff888061894070 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520003f2e30 R12: ffff88805fd330b0
R13: 1ffff1100c31280f R14: 1ffff1100c31280e R15: ffff888061894078
FS:  0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33e1cff8 CR3: 0000000072838000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lookup_object_or_alloc lib/debugobjects.c:591 [inline]
 debug_object_activate+0x13a/0x4e0 lib/debugobjects.c:696
 debug_rcu_head_queue kernel/rcu/rcu.h:176 [inline]
 kvfree_call_rcu+0xb0/0x7f0 kernel/rcu/tree.c:3591
 cfg80211_update_known_bss+0x184/0xb60 net/wireless/scan.c:-1
 cfg80211_bss_update+0x156/0x21a0 net/wireless/scan.c:1830
 cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2552 [inline]
 cfg80211_inform_bss_frame_data+0x88d/0x1ed0 net/wireless/scan.c:2585
 ieee80211_bss_info_update+0x6ba/0xa80 net/mac80211/scan.c:190
 ieee80211_rx_bss_info net/mac80211/ibss.c:1123 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1614 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x1763/0x2b50 net/mac80211/ibss.c:1643
 ieee80211_iface_process_skb net/mac80211/iface.c:1459 [inline]
 ieee80211_iface_work+0x714/0xc50 net/mac80211/iface.c:1513
 cfg80211_wiphy_work+0x224/0x260 net/wireless/core.c:433
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/28 02:22 linux-5.15.y 674f684f7c61 45ae1df4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in write_ports
2026/07/27 21:59 linux-5.15.y 674f684f7c61 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in write_ports
* Struck through repros no longer work on HEAD.