INFO: task hung in synchronize_rcu (4)

Status: upstream: reported C repro on 2023/05/04 02:01
Subsystems: fs net
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+222aa26d0a5dbc2e84fe@syzkaller.appspotmail.com
First crash: 1238d, last: 2h25m
Cause bisection: introduced by (bisect log) :
commit 3b5d4ddf8fe1f60082513f94bae586ac80188a03
Author: Martin KaFai Lau <kafai@fb.com>
Date: Wed Mar 9 09:04:50 2022 +0000

  bpf: net: Remove TC_AT_INGRESS_OFFSET and SKB_MONO_DELIVERY_TIME_OFFSET macro

Crash: INFO: task hung in synchronize_rcu (log)
Repro: syz .config
  
Fix bisection: failed (error log, bisect log)
  
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
1ea8e1d5 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: task hung in synchronize_rcu (4) 2026/05/24 19:53 2026/05/24 19:53 2026/05/24 20:29 c69befb3
Discussions (20)
Title Replies (including bot) Last reply
[syzbot] Monthly net report (Jul 2026) 0 (1) 2026/07/25 04:32
[syzbot] Monthly fs report (Jul 2026) 0 (1) 2026/07/10 20:32
[syzbot] Monthly fs report (Jun 2026) 0 (1) 2026/06/09 20:32
[syzbot] Monthly fs report (May 2026) 0 (1) 2026/05/09 12:32
[syzbot] Monthly net report (Apr 2026) 0 (1) 2026/04/22 09:08
[syzbot] Monthly net report (Mar 2026) 0 (1) 2026/03/23 09:11
[syzbot] Monthly fs report (Mar 2026) 0 (1) 2026/03/06 11:53
[syzbot] Monthly net report (Feb 2026) 0 (1) 2026/02/18 13:21
[syzbot] Monthly net report (Jan 2026) 2 (3) 2026/01/20 11:17
[syzbot] Monthly fs report (Dec 2025) 0 (1) 2025/12/01 12:38
[syzbot] Monthly fs report (Sep 2025) 0 (1) 2025/09/30 07:56
[syzbot] Monthly net report (Aug 2024) 0 (1) 2024/08/02 07:26
[syzbot] Monthly fs report (Jul 2024) 0 (1) 2024/07/18 07:59
[syzbot] Monthly fs report (Mar 2024) 0 (1) 2024/03/16 12:09
[syzbot] Monthly fs report (Feb 2024) 0 (1) 2024/02/12 21:31
[syzbot] Monthly fs report (Dec 2023) 0 (1) 2023/12/12 22:02
[syzbot] Monthly fs report (Aug 2023) 0 (1) 2023/08/08 12:55
[syzbot] Monthly fs report (Jul 2023) 0 (1) 2023/07/10 09:36
[syzbot] [fs?] INFO: task hung in synchronize_rcu (4) 2 (4) 2023/05/21 05:04
Re: [syzbot] [fs?] INFO: task hung in synchronize_rcu (4) 4 (4) 2023/05/05 09:49
Similar bugs (16)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in synchronize_rcu (3) 1 syz, C done done 374 1272d 2209d 22/29 fixed on 2023/02/24 13:50
linux-6.1 INFO: task hung in synchronize_rcu origin:lts-only 1 syz, C unreliable 58 1d23h 1227d 0/3 upstream: reported C repro on 2023/04/01 04:49
android-6-12 INFO: task hung in synchronize_rcu (3) 1 3 3d11h 30d 0/1 premoderation: reported on 2026/07/10 14:29
android-49 INFO: task hung in synchronize_rcu 1 1 2445d 2445d 0/3 auto-closed as invalid on 2020/03/28 16:57
linux-4.14 INFO: task hung in synchronize_rcu vfs 1 syz, C error 162 1286d 2468d 0/1 upstream: reported C repro on 2019/11/07 04:32
linux-4.19 INFO: task hung in synchronize_rcu 1 syz, C error 70 1275d 2466d 0/1 upstream: reported C repro on 2019/11/08 21:27
linux-5.15 INFO: task hung in synchronize_rcu 1 1 1212d 1212d 0/3 auto-obsoleted due to no activity on 2023/08/14 02:05
android-6-12 INFO: task hung in synchronize_rcu 1 41 270d 394d 0/1 auto-obsoleted due to no activity on 2026/01/01 15:51
linux-5.15 INFO: task hung in synchronize_rcu (3) origin:lts-only 1 syz, C error 56 17d 745d 0/3 upstream: reported C repro on 2024/07/26 03:55
upstream INFO: task hung in synchronize_rcu 1 syz done 1206 2445d 2472d 14/29 fixed on 2019/11/29 15:48
linux-5.15 INFO: task hung in synchronize_rcu (2) 1 1 900d 900d 0/3 auto-obsoleted due to no activity on 2024/05/31 13:53
android-414 INFO: task hung in synchronize_rcu 1 1 2463d 2463d 0/1 auto-closed as invalid on 2020/03/10 10:42
upstream INFO: task hung in synchronize_rcu (2) trace 1 8 2444d 2445d 0/29 closed as invalid on 2019/11/30 16:54
linux-6.6 INFO: task hung in synchronize_rcu 1 11 3d11h 283d 0/2 upstream: reported on 2025/10/30 17:16
android-6-12 INFO: task hung in synchronize_rcu (2) 1 5 135d 176d 0/1 auto-obsoleted due to no activity on 2026/06/25 10:28
upstream INFO: task hung in rtnetlink_rcv_msg net 1 syz, C inconclusive inconclusive 1970 762d 2725d 26/29 fixed on 2024/07/09 19:14
Last patch testing requests (15)
Created Duration User Patch Repo Result
2025/08/17 18:52 22m retest repro https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing report log
2025/02/15 20:25 30m retest repro upstream OK log
2025/02/15 08:25 27m retest repro upstream OK log
2024/04/21 13:23 22m retest repro upstream report log
2024/04/21 13:23 29m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK log
2024/02/20 14:30 26m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK log
2024/02/20 14:30 25m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK log
2024/02/20 14:30 28m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK log
2024/01/14 18:13 22m retest repro upstream report log
2023/08/28 15:24 45m (2) retest repro upstream OK log
2023/05/25 12:07 18m penguin-kernel@i-love.sakura.ne.jp patch upstream report log
2023/05/25 11:18 22m penguin-kernel@i-love.sakura.ne.jp patch upstream OK log
2023/05/25 10:47 21m penguin-kernel@i-love.sakura.ne.jp patch upstream OK log
2023/05/24 02:02 30m penguin-kernel@i-love.sakura.ne.jp patch upstream report log
2023/05/23 13:13 19m penguin-kernel@i-love.sakura.ne.jp patch upstream error

Sample crash report:
INFO: task pool_workqueue_:3 blocked for more than 40 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:pool_workqueue_ state:D stack:28024 pid:3     tgid:3     ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x11f6/0x6500 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
 synchronize_rcu_normal+0x230/0x260 kernel/rcu/tree.c:3333
 synchronize_rcu_expedited+0x3cd/0x450 kernel/rcu/tree_exp.h:955
 wq_unregister_lockdep kernel/workqueue.c:4949 [inline]
 pwq_release_workfn+0x618/0xb30 kernel/workqueue.c:5245
 kthread_worker_fn+0x300/0xbe0 kernel/kthread.c:1025
 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>
INFO: task kworker/1:0:31 blocked for more than 40 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:0     state:D stack:23320 pid:31    tgid:31    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_power_efficient crda_timeout_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x11f6/0x6500 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 rt_mutex_schedule+0x96/0xe0 kernel/sched/core.c:7607
 rt_mutex_slowlock_block.constprop.0+0x366/0x7c0 kernel/locking/rtmutex.c:1670
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1747 [inline]
 __rt_mutex_slowlock_locked.constprop.0+0x1cc/0x760 kernel/locking/rtmutex.c:1787
 rt_mutex_slowlock.constprop.0+0x8d/0x120 kernel/locking/rtmutex.c:1827
 __rt_mutex_lock kernel/locking/rtmutex.c:1842 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:560 [inline]
 mutex_lock_nested+0xd6/0x110 kernel/locking/rtmutex_api.c:578
 crda_timeout_work+0x16/0x70 net/wireless/reg.c:529
 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>
INFO: task kworker/u8:7:167 blocked for more than 40 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:7    state:D stack:22608 pid:167   tgid:167   ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x11f6/0x6500 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
 synchronize_rcu_normal+0x230/0x260 kernel/rcu/tree.c:3333
 synchronize_rcu_expedited+0x3cd/0x450 kernel/rcu/tree_exp.h:955
 synchronize_net net/core/dev.c:12276 [inline]
 dev_remove_pack+0x7a/0xb0 net/core/dev.c:689
 tipc_detach_loopback+0x5b/0x110 net/tipc/bearer.c:819
 tipc_exit_net+0x8b/0x260 net/tipc/core.c:112
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
 cleanup_net+0x49c/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/0[  163.797520][   T38]  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
4 locks held by ktimers/0/16:
3 locks held by pr/legacy/17:
2 locks held by rcu_preempt/18:
3 locks held by kworker/1:0/31:
 #0: ffff88813fe3e538 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc90000a5fd08 ((crda_timeout).work){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff8fd25398 (rtnl_mutex){+.+.}-{4:4}, at: crda_timeout_work+0x16/0x70 net/wireless/reg.c:529
1 lock held by khungtaskd/38:
 #0: ffffffff8e04e740 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8e04e740 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8e04e740 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by kcompactd0/41:
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:779 [inline]
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x223/0x660 lib/debugobjects.c:758
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x149/0x4e0 mm/slub.c:3817
2 locks held by kcompactd1/42:
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:779 [inline]
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x223/0x660 lib/debugobjects.c:758
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x149/0x4e0 mm/slub.c:3817
7 locks held by kworker/u8:4/66:
2 locks held by kworker/0:1H/102:
7 locks held by kworker/u8:5/122:
3 locks held by kworker/u8:7/167:
 #0: ffff88801bae0938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900038ffd08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff8fd0cc60 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:673
2 locks held by dhcpcd/5248:
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:779 [inline]
 #0: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x223/0x660 lib/debugobjects.c:758
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #1: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x149/0x4e0 mm/slub.c:3817
2 locks held by getty/5341:
 #0: ffff8880384d30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003cc62e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x424/0x14f0 drivers/tty/n_tty.c:2211
4 locks held by udevd/5614:
3 locks held by kworker/1:4/5645:
1 lock held by syz-executor663/5977:
2 locks held by syz-executor663/6203:
2 locks held by syz-executor663/6205:
2 locks held by syz-executor663/6207:
 #0: ffffffff8fd0cc60 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff8fd25398 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x21e/0x780 net/ipv4/ip_tunnel.c:1149
2 locks held by syz-executor663/6209:
1 lock held by dhcpcd/6211:
 #0: ffff88803e628358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803e628358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6212:
 #0: ffff88803b75e358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803b75e358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6213:
 #0: ffff88803c2bc358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803c2bc358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
3 locks held by dhcpcd/6214:
 #0: ffff88802eceacb0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_downgrade include/linux/mmap_lock.h:586 [inline]
 #0: ffff88802eceacb0 (&mm->mmap_lock){++++}-{4:4}, at: vms_complete_munmap_vmas+0x946/0xdd0 mm/vma.c:1340
 #1: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:779 [inline]
 #1: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x223/0x660 lib/debugobjects.c:758
 #2: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #2: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x149/0x4e0 mm/slub.c:3817
1 lock held by dhcpcd/6215:
 #0: ffff88803c2b8358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803c2b8358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6216:
 #0: ffff88803c2be358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803c2be358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6217:
 #0: ffff88803b534358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803b534358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6218:
 #0: ffff88803b4a8358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803b4a8358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
1 lock held by dhcpcd/6219:
 #0: ffff88803b4aa358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
 #0: ffff88803b4aa358 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3226
3 locks held by dhcpcd/6220:
 #0: ffff888032b6acb0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:554 [inline]
 #0: ffff888032b6acb0 (&mm->mmap_lock){++++}-{4:4}, at: __vm_munmap+0x10f/0x390 mm/vma.c:3285
 #1: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:779 [inline]
 #1: ffffffff8ebe21a0 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool+0x223/0x660 lib/debugobjects.c:758
 #2: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
 #2: ffff88813fe20758 (&n->list_lock){+.+.}-{3:3}, at: get_from_partial_node+0x149/0x4e0 mm/slub.c:3817

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5977 Comm: syz-executor663 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:write_comp_data+0x2e/0xa0 kernel/kcov.c:246
Code: 89 cf 49 89 d2 65 8b 15 20 a2 53 11 65 48 8b 0d 00 a2 53 11 49 89 f1 81 e2 00 00 ff 00 8b 81 f4 0b 00 00 89 d6 25 00 01 00 00 <09> c6 74 17 85 c0 74 04 85 d2 74 05 c3 cc cc cc cc 8b 81 f4 16 00
RSP: 0018:ffffc900038cf6e0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88803870d200 RCX: ffff888027d98000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8b0988ac
RBP: 000000000000000b R08: 0000000000000000 R09: 0000000000000007
R10: 000000000000000b R11: 0000000000000000 R12: ffff888041231b40
R13: 0000000000000007 R14: 0000000000000001 R15: 0000000000000000
FS:  000055556f5b4400(0000) GS:ffff888125097000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2474af7d3c CR3: 000000003d734000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 mt_validate_nulls+0x48c/0xa20 lib/maple_tree.c:6908
 mt_validate+0x188d/0x3220 lib/maple_tree.c:6956
 validate_mm+0xa8/0x4e0 mm/vma.c:652
 mmap_region+0x38d/0x620 mm/vma.c:2866
 do_mmap+0xc74/0x1300 mm/mmap.c:560
 vm_mmap_pgoff+0x2a4/0x470 mm/util.c:581
 ksys_mmap_pgoff+0x3d1/0x620 mm/mmap.c:606
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
 __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0x830 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2474a89122
Code: 00 00 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 6e 5b 5d c3 0f 1f 00 48 c7 c0 d0 ff ff ff 64
RSP: 002b:00007ffc98fd5ca8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000001b2e964000 RCX: 00007f2474a89122
RDX: 0000000000000003 RSI: 00000000005c0000 RDI: 0000001b2e964000
RBP: 0000000000100001 R08: 0000000000000003 R09: 0000000000040000
R10: 0000000000100001 R11: 0000000000000206 R12: 00007ffc98fd5cc0
R13: 0000000000000002 R14: 00007f2474b27560 R15: 0000000000000002
 </TASK>

Crashes (4265):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/07 14:18 upstream f9a2394a2348 75707236 .config console log report C ci-upstream-kasan-gce-selinux-root INFO: task hung in synchronize_rcu
2026/07/27 10:34 upstream 4235cb24ec1e 492bab15 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: task hung in synchronize_rcu
2025/07/28 07:27 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 51d4b0a44c82 fb8f743d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-upstream-usb INFO: task hung in synchronize_rcu
2026/02/05 03:23 net-next 9a9424c756fe ea10c935 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: task hung in synchronize_rcu
2023/07/05 16:36 net 3674fbf0451d 80298b6f .config strace log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: task hung in synchronize_rcu
2023/07/05 16:01 net-next ae230642190a 80298b6f .config strace log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: task hung in synchronize_rcu
2023/05/20 22:13 net-next dcbe4ea1985d 4bce1a3e .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: task hung in synchronize_rcu
2024/04/07 11:39 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 707081b61156 ca620dd8 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-gce-arm64 INFO: task hung in synchronize_rcu
2023/12/28 18:06 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci aafe7ad77b91 fb427a07 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-gce-arm64 INFO: task hung in synchronize_rcu
2023/12/27 22:32 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci aafe7ad77b91 fb427a07 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-gce-arm64 INFO: task hung in synchronize_rcu
2023/12/21 08:08 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci aafe7ad77b91 4f9530a3 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-gce-arm64 INFO: task hung in synchronize_rcu
2023/05/15 07:26 upstream 838a854820ee 2b9ba477 .config strace log report syz [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: task hung in synchronize_rcu
2023/04/30 01:55 net 6686317855c6 62df2017 .config console log report syz [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: task hung in synchronize_rcu
2026/08/07 11:18 upstream f9a2394a2348 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: task hung in synchronize_rcu
2026/04/09 10:55 upstream 7f87a5ea75f0 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: task hung in synchronize_rcu
2026/03/24 05:48 upstream c369299895a5 baf8bf12 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: task hung in synchronize_rcu
2025/03/22 17:58 upstream 88d324e69ea9 c6512ef7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs INFO: task hung in synchronize_rcu
2025/01/18 23:06 upstream fda5e3f28400 f2cb035c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in synchronize_rcu
2024/09/23 06:10 upstream a430d95c5efa 6f888b75 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: task hung in synchronize_rcu
2023/12/27 13:24 upstream fbafc3e621c3 fb427a07 .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: task hung in synchronize_rcu
2026/07/23 20:10 upstream 4539944e5151 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: task hung in synchronize_rcu
2023/04/09 04:38 upstream a79d5c76f705 71147e29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: task hung in synchronize_rcu
2026/08/06 02:53 net 9113e98eb7e3 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: task hung in synchronize_rcu
2026/07/19 05:24 net-next ce6b4d3216b6 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: task hung in synchronize_rcu
2026/08/06 00:01 linux-next cc2b5f627e8c cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: task hung in synchronize_rcu
2026/08/05 20:54 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 5d5fd841c346 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb INFO: task hung in synchronize_rcu
2026/03/24 14:44 linux-next 09c0f7f1bcdb 74e70d19 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: task hung in synchronize_rcu
2026/08/10 07:51 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/10 06:46 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/09 21:25 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/09 19:20 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/09 15:09 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/09 13:54 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/09 09:08 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next ed8384586cf9 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/08 04:08 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 5d63f80b .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/07 18:00 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 e4ef95d6 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/07 15:46 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 e4ef95d6 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/07 13:27 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 e4ef95d6 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/07 04:12 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 c38879ea .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 16:22 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cc56899a .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 13:08 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cc56899a .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 09:29 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cd5b1963 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 07:35 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cd5b1963 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 06:20 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cd5b1963 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/06 05:15 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 8f77fefb5fa2 cd5b1963 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/05 14:39 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 1eed00d1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/05 09:17 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 52aa2820 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/05 06:12 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 52aa2820 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/05 05:09 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 52aa2820 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/05 03:42 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 52aa2820 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/04 21:01 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 3c5eaa21 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/04 17:01 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 3c5eaa21 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/04 15:44 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 3c5eaa21 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/04 06:48 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 9451e17e .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 18:59 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 bdd50915 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 17:48 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 bdd50915 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 15:29 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 bdd50915 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 09:02 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 08:01 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 06:50 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 05:03 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 01:55 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/03 00:08 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 22:42 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 21:12 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 18:56 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 17:33 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 15:45 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 13:07 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 09:57 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 09:02 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/08/02 04:31 git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next 320840b34af2 e611ffe1 .config console log report info ci-qemu-native-arm64-kvm INFO: task hung in synchronize_rcu
2026/07/30 22:00 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 365f9c7a6b81 aaffb173 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 INFO: task hung in synchronize_rcu
2026/06/30 20:09 https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux master dc59e4fea9d8 e5173a01 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm32 INFO: task hung in synchronize_rcu
* Struck through repros no longer work on HEAD.