INFO: task hung in afs_cell_purge (2)

Status: auto-obsoleted due to no activity on 2026/10/03 10:33
Subsystems: afs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+750f21d691e244b473b1@syzkaller.appspotmail.com
First crash: 557d, last: 91d
Cause bisection: introduced by (bisect log) :
commit 1d0b929fc070b4115403a0a6206a0c6a62dd61f5
Author: David Howells <dhowells@redhat.com>
Date: Mon Feb 24 09:52:58 2025 +0000

  afs: Change dynroot to create contents on demand

Crash: BUG: unable to handle kernel NULL pointer dereference in afs_dynroot_d_release (log)
Repro: syz .config
  
Fix bisection: fixed by (bisect log) :
commit c9c3b615a462a4023bd148f02c564e175ed10502
Author: David Howells <dhowells@redhat.com>
Date: Mon Jun 22 09:08:45 2026 +0000

  afs: Fix misplaced inc of net->cells_outstanding

  
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
7cf6d2da assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: task hung in afs_cell_purge (2) 2026/05/12 23:19 2026/05/12 23:19 2026/05/12 23:59 ac1aeadb
▶ ▼ Discussions (11)
Title Replies (including bot) Last reply
[syzbot] [afs?] INFO: task hung in afs_cell_purge (2) 3 (8) 2026/08/04 13:08
[syzbot] Monthly afs report (Jul 2026) 0 (1) 2026/07/17 04:32
[syzbot] Monthly afs report (Jun 2026) 0 (1) 2026/06/15 20:32
[syzbot] Monthly afs report (May 2026) 0 (1) 2026/05/05 04:32
[syzbot] Monthly afs report (Jan 2026) 0 (1) 2026/01/20 20:43
[syzbot] Monthly afs report (Dec 2025) 0 (1) 2025/12/20 15:59
[syzbot] Monthly afs report (Nov 2025) 0 (1) 2025/11/19 12:55
[syzbot] Monthly afs report (Oct 2025) 0 (1) 2025/10/10 07:31
[syzbot] Monthly afs report (Jul 2025) 0 (1) 2025/07/21 07:59
[syzbot] Monthly afs report (Jun 2025) 0 (1) 2025/06/20 09:32
[syzbot] Monthly afs report (May 2025) 0 (1) 2025/05/20 07:44
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in afs_cell_purge afs 1 1 1199d 1199d 0/29 auto-obsoleted due to no activity on 2023/09/20 16:02
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/10/03 09:58 34m retest repro linux-next no crash job log log
2026/07/22 12:50 43m retest repro linux-next error
2026/07/19 13:55 18m retest repro upstream log
2026/06/16 16:06 3h42m dhowells@redhat.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git v7.1 log
2025/06/08 05:46 19m hdanton@sina.com patch upstream OK log

Sample crash report:
INFO: task kworker/u10:16:16937 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u10:16  state:D stack:22984 pid:16937 tgid:16937 ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 afs_cell_purge+0x46a/0x550 fs/afs/cell.c:921
 afs_net_exit+0x83/0x150 fs/afs/main.c:147
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
 cleanup_net+0x499/0x920 net/core/net_namespace.c:702
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
3 locks held by kworker/u10:16/16937:
 #0: ffff88801caf6140 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc90003787d08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff90a84f68 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:673
2 locks held by kworker/u10:24/16976:
 #0: ffff88801e313940 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc90003ecfd08 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
2 locks held by getty/19137:
 #0: ffff888036f580a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90005c032e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
3 locks held by syz.2.3052/22037:
 #0: ffffffff90a84f68 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff90a9db80 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #1: ffffffff90a9db80 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
 #2: ffffffff8ebf19a8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
2 locks held by syz.1.3054/22036:
 #0: ffffffff90a84f68 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff8ebf19a8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311
2 locks held by syz.4.3055/22045:
 #0: ffffffff90a84f68 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff90a9db80 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x21e/0x780 net/ipv4/ip_tunnel.c:1149
2 locks held by syz.4.3055/22047:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:122
 nmi_trigger_cpumask_backtrace+0x21c/0x2a0 lib/nmi_backtrace.c:65
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (322):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/04 01:45 upstream d2c9a99135da aa437a8a .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/07/03 02:10 upstream 4a50a141f05a 2b70b115 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/30 19:59 upstream dc59e4fea9d8 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/06/30 04:18 upstream dc59e4fea9d8 fff8d0a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/06/28 22:59 upstream 8b69c0475871 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/28 10:38 upstream 780d569e6c4b fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/24 07:47 upstream f31c00c377cc 042555ff .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: task hung in afs_cell_purge
2026/06/24 03:37 upstream 558ef39aeb9a 042555ff .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/06/23 19:10 upstream 502d801f0ab0 4b1d8f01 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/23 16:08 upstream 502d801f0ab0 4b1d8f01 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/23 01:30 upstream ef0c9f75a195 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in afs_cell_purge
2026/06/22 19:31 upstream ef0c9f75a195 ab2703f0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/22 04:47 upstream 8cd8cf7a07e5 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/22 03:39 upstream 8cd8cf7a07e5 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in afs_cell_purge
2026/06/22 00:33 upstream 8cd8cf7a07e5 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/21 22:50 upstream 8cd8cf7a07e5 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/21 13:10 upstream 390d73adf896 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in afs_cell_purge
2026/06/20 20:40 upstream 1a3746ccbb0a 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: task hung in afs_cell_purge
2026/06/18 06:23 upstream e771677c937d b62b3ded .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/06/15 22:41 upstream 0e0611827f33 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/06/11 16:24 upstream 9716c086c8e8 d93a6ab6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/06/11 15:13 upstream 9716c086c8e8 d93a6ab6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/06/10 16:06 upstream acb7500801e9 f79bac11 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/06/02 01:46 upstream e43ffb69e043 1095583b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/06/01 03:32 upstream 8d9c51eac648 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/28 05:22 upstream eb3f4b7426cf 4c36e7e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/05/27 14:52 upstream eb3f4b7426cf 769cbc61 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/27 12:42 upstream eb3f4b7426cf 8777bdc3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/05/26 06:10 upstream e8c2f9fdadee c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/22 13:33 upstream 6779b50faa56 e16cf9f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/18 16:39 upstream 5200f5f493f7 55156e84 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/16 00:16 upstream d458a240344c 81fb92f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/14 03:18 upstream e1914add2799 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/12 03:34 upstream 50897c955902 d168f260 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/10 11:32 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: task hung in afs_cell_purge
2026/05/10 02:11 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/07 18:41 upstream 8ab992f815d6 cbf9e0fc .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/05/06 08:34 upstream 9207d47f966b 26da2c66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2026/05/04 13:50 upstream 6d35786de281 85f1bcf2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in afs_cell_purge
2025/05/01 06:21 upstream 7a13c14ee59d ce7952f4 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-upstream-fs INFO: task hung in afs_cell_purge
2026/06/28 13:21 upstream 780d569e6c4b fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/06/16 00:07 upstream 0e0611827f33 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/06/03 18:06 upstream ba3e43a9e601 234057e5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/31 15:31 upstream 174914ea5513 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/28 08:54 upstream eb3f4b7426cf 4c36e7e5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/27 17:25 upstream eb3f4b7426cf 769cbc61 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/25 07:35 upstream 6a97c4d5262d c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/13 18:51 upstream 1d5dcaa3bd65 fec2a7ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/05/07 16:40 upstream 5862221fdded f250db59 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in afs_cell_purge
2026/06/30 23:55 linux-next 7de6ae9e1220 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: task hung in afs_cell_purge
2026/06/20 15:27 linux-next ec039126b7fa 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: task hung in afs_cell_purge
2026/02/16 14:48 linux-next 635c467cc14e 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root INFO: task hung in afs_cell_purge
2026/02/16 09:37 linux-next 635c467cc14e 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in afs_cell_purge
* Struck through repros no longer work on HEAD.