INFO: rcu detected stall in kcov_close (2)

Status: upstream: reported on 2026/05/21 10:08
Reported-by: syzbot+5471950bb80340c1d274@syzkaller.appspotmail.com
First crash: 137d, last: 1d13h
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in kcov_close 1 6 811d 862d 0/3 auto-obsoleted due to no activity on 2024/10/23 16:14
upstream INFO: rcu detected stall in kcov_close prio:normal mm 1 253 6d14h 784d 0/29 upstream: reported on 2024/08/12 12:28
linux-6.6 INFO: rcu detected stall in kcov_close 1 1 288d 288d 0/2 auto-obsoleted due to no activity on 2026/03/31 08:37
linux-5.15 BUG: soft lockup in kcov_close 1 1 862d 862d 0/3 auto-obsoleted due to no activity on 2024/09/03 09:36
upstream INFO: task hung in release_tty (3) serial 1 3 695d 761d 0/29 auto-obsoleted due to no activity on 2025/02/07 03:06

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5140/1:b..l P16415/1:b..l P25023/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=206225, q=429 ncpus=1)
task:syz-executor    state:R  running task     stack:24360 pid:25023 ppid:5763   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6868
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6892
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 unwind_next_frame+0x201c/0x2990 arch/x86/kernel/unwind_orc.c:672
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x319/0x400 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
 kmem_cache_zalloc include/linux/slab.h:711 [inline]
 lsm_file_alloc security/security.c:625 [inline]
 security_file_alloc+0x34/0x120 security/security.c:2640
 init_file+0x94/0x1f0 fs/file_table.c:179
 alloc_empty_file+0xb7/0x1d0 fs/file_table.c:228
 path_openat+0x120/0x3270 fs/namei.c:3830
 do_filp_open+0x1f2/0x430 fs/namei.c:3871
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8b1df592d7
RSP: 002b:00007ffd84660c70 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000555566ea6500 RCX: 00007f8b1df592d7
RDX: 0000000000000002 RSI: 00007f8b1e034733 RDI: ffffffffffffff9c
RBP: 00007f8b1e2265d8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000003 R14: 00007ffd84660f68 R15: 0000000000000000
 </TASK>
task:syz-executor    state:R  running task     stack:21800 pid:16415 ppid:1      flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7011
 irqentry_exit+0x67/0x70 kernel/entry/common.c:441
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:211
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d fc d3 04 0d 48 89 de 5b e9 f3 d6 57 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d 40 27 7c 7e 65 8b 15 41 27 7c 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc900033d7580 EFLAGS: 00000202
RAX: ffffffff813322f2 RBX: ffffc900033d7640 RCX: ffff888025065a00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc900033d7610 R08: ffff888025065a00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff81d27f57
R13: 1ffff11004a0cbef R14: ffffffff81762b60 R15: ffffc900033d7588
 arch_stack_walk+0x152/0x190 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 vfree+0x1a7/0x340 mm/vmalloc.c:2899
 kcov_put kernel/kcov.c:440 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:536
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x986/0x2530 kernel/exit.c:890
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 get_signal+0x12a6/0x1390 kernel/signal.c:2915
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:294 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:305
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6bfdd5e98e
RSP: 002b:00007fffcbfb0c28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: 0000000000000000 RBX: 0000555561806500 RCX: 00007f6bfdd5e98e
RDX: 0000000000000030 RSI: 00007fffcbfb0d20 RDI: 00000000000000f9
RBP: 00007fffcbfb0ccc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000025c
R13: 00000000000927c0 R14: 0000000000205c79 R15: 00007fffcbfb0d20
 </TASK>
task:udevd           state:R  running task     stack:23176 pid:5140  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7011
 irqentry_exit+0x67/0x70 kernel/entry/common.c:441
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__sanitizer_cov_trace_pc+0x5c/0x60 kernel/kcov.c:230
Code: 00 16 00 00 83 fa 02 75 21 48 8b 91 08 16 00 00 48 8b 32 48 8d 7e 01 8b 89 04 16 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2 08 <c3> 0f 1f 00 f3 0f 1e fa 48 8b 04 24 65 48 8b 15 e0 26 7c 7e 65 8b
RSP: 0018:ffffc900032c7458 EFLAGS: 00000293
RAX: ffffffff813bb2a1 RBX: ffffc900032c74d0 RCX: ffff88807e693c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff88807e693c00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff83ed8023
R13: 1ffff1100fcd282f R14: dffffc0000000000 R15: 1ffff92000658e9a
 unwind_get_return_address+0x71/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 __slab_free+0x35a/0x400 mm/slub.c:3736
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 ____kasan_kmalloc mm/kasan/common.c:341 [inline]
 __kasan_kmalloc+0x22/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 tomoyo_realpath_from_path+0xe6/0x5c0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x282/0x560 security/tomoyo/file.c:822
 security_inode_getattr+0xd3/0x120 security/security.c:2190
 vfs_getattr fs/stat.c:173 [inline]
 vfs_statx+0x172/0x680 fs/stat.c:248
 vfs_fstatat+0x12a/0x1b0 fs/stat.c:299
 __do_sys_newfstatat fs/stat.c:463 [inline]
 __se_sys_newfstatat fs/stat.c:457 [inline]
 __x64_sys_newfstatat+0x149/0x1f0 fs/stat.c:457
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe88a111b0a
RSP: 002b:00007ffeed98f9a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00005580bf49c410 RCX: 00007fe88a111b0a
RDX: 00007ffeed98f9b0 RSI: 00005580bf48a2a8 RDI: 00000000ffffff9c
RBP: 00005580eecfa148 R08: 00063478c1c69200 R09: 0000000000745bdb
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffeed98f9b0 R14: 0000000000000000 R15: 00063478c1c69200
 </TASK>
rcu: rcu_preempt kthread starved for 9439 jiffies! g206225 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26824 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 3382 Comm: kworker/R-bat_e Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: bat_events batadv_tt_purge
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xc0/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> ab 96 c0 f6 65 8b 05 1c 54 67 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900000079a0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 07d1c0d79158dc00
RDX: dffffc0000000000 RSI: ffffffff8acacce0 RDI: 0000000000000001
RBP: ffffc90000007a30 R08: ffffffff911f0607 R09: 1ffffffff223e0c0
R10: dffffc0000000000 R11: fffffbfff223e0c1 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888142fb8000 R15: 1ffff92000000f34
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f456f0688d2 CR3: 00000000770a8000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 dummy_timer+0x3170/0x34e0 drivers/usb/gadget/udc/dummy_hcd.c:-1
 __run_hrtimer kernel/time/hrtimer.c:1754 [inline]
 __hrtimer_run_queues+0x525/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_run_softirq+0x177/0x290 kernel/time/hrtimer.c:1835
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 do_softirq+0xfa/0x1a0 kernel/softirq.c:479
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x184/0x1c0 kernel/softirq.c:406
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_tt_global_purge net/batman-adv/translation-table.c:2359 [inline]
 batadv_tt_purge+0x4b5/0xa20 net/batman-adv/translation-table.c:3633
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 rescuer_thread+0x71e/0x1080 kernel/workqueue.c:2931
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/04 01:27 linux-6.6.y a91a6aa9253c 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_close
2026/09/17 08:39 linux-6.6.y 79643295eba1 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_close
2026/08/21 05:05 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_close
2026/05/24 05:59 linux-6.6.y 0a40c6fbd105 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_close
2026/05/21 10:07 linux-6.6.y eac8889a3a1c 41b8c833 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_close
* Struck through repros no longer work on HEAD.