INFO: rcu detected stall in kcov_mmap

Status: auto-obsoleted due to no activity on 2026/03/29 04:54
Reported-by: syzbot+d17c0acd83b5c24a2411@syzkaller.appspotmail.com
First crash: 259d, last: 236d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in kcov_mmap (2) mm 1 18 477d 798d 0/29 auto-obsoleted due to no activity on 2025/07/20 12:30
linux-5.15 INFO: rcu detected stall in kcov_mmap 1 3 718d 810d 0/3 auto-obsoleted due to no activity on 2024/12/01 17:49
upstream INFO: rcu detected stall in kcov_mmap mm 1 1 910d 910d 0/29 auto-obsoleted due to no activity on 2024/05/13 16:16
linux-6.1 INFO: rcu detected stall in kcov_mmap 1 1 748d 748d 0/3 auto-obsoleted due to no activity on 2024/11/01 05:49
upstream BUG: soft lockup in kcov_mmap mm 1 1 1949d 1945d 0/29 auto-closed as invalid on 2021/07/09 11:42

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P8058/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=30797, q=257 ncpus=2)
task:syz-executor    state:R  running task     stack:24232 pid:8058  ppid:5751   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x1f2/0x410 kernel/locking/lockdep.c:5758
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00
RSP: 0018:ffffc90010d07760 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 09a97b7698eda600
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc6f80
RBP: ffffc90010d07868 R08: dffffc0000000000 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: 1ffff920021a0ef8
R13: ffffffff8cd2ff20 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 __pte_offset_map+0x48/0x2c0 mm/pgtable-generic.c:287
 __pte_offset_map_lock+0x47/0x1e0 mm/pgtable-generic.c:371
 pte_offset_map_lock include/linux/mm.h:3016 [inline]
 __get_locked_pte mm/memory.c:1823 [inline]
 get_locked_pte include/linux/mm.h:2741 [inline]
 insert_page mm/memory.c:1865 [inline]
 vm_insert_page+0x548/0x8b0 mm/memory.c:2021
 kcov_mmap+0xe9/0x160 kernel/kcov.c:505
 call_mmap include/linux/fs.h:2023 [inline]
 mmap_file mm/internal.h:98 [inline]
 __mmap_region mm/mmap.c:2790 [inline]
 mmap_region+0xfa5/0x2020 mm/mmap.c:2941
 do_mmap+0x92f/0x10a0 mm/mmap.c:1385
 vm_mmap_pgoff+0x1c0/0x400 mm/util.c:556
 ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fea22d8f783
RSP: 002b:00007fff0b095dc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fea22fe6038 RCX: 00007fea22d8f783
RDX: 0000000000000003 RSI: 0000000000400000 RDI: 00007fea227ff000
RBP: 00007fea22fe6038 R08: 00000000000000d8 R09: 0000000000000000
R10: 0000000000000011 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000003 R14: 00007fff0b0960b8 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10535 jiffies! g30797 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:27704 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8052 Comm: syz.3.470 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:212
Code: 00 0f 0b 0f 1f 80 00 00 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d 9c 92 c4 0c 48 89 de 5b e9 43 9d 56 00 cc cc cc <f3> 0f 1e fa 48 8b 04 24 65 48 8b 0d f0 24 7e 7e 65 8b 15 f1 24 7e
RSP: 0018:ffffc90000007870 EFLAGS: 00000002
RAX: ffffffff8e5e8d14 RBX: ffffffff8e5e8d18 RCX: ffff88802b57da00
RDX: 0000000000010000 RSI: ffffffff81927b54 RDI: ffffffff81927a8e
RBP: ffffffff8e5e8d18 R08: ffffc90000007a10 R09: 0000000000000008
R10: 0000000000000004 R11: 0000000000010000 R12: ffffffff8e5e8d1c
R13: ffffffff81927a8e R14: ffffffff81927b54 R15: ffffffff8e5e8d18
FS:  00007f6d705b46c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1f9e6aef98 CR3: 0000000024200000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 __orc_find arch/x86/kernel/unwind_orc.c:99 [inline]
 orc_find arch/x86/kernel/unwind_orc.c:227 [inline]
 unwind_next_frame+0x501/0x2970 arch/x86/kernel/unwind_orc.c:494
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 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+0x11e/0x2e0 mm/slub.c:3519
 __sigqueue_alloc+0x40c/0x520 kernel/signal.c:438
 __send_signal_locked+0x22f/0xe00 kernel/signal.c:1130
 do_send_sig_info kernel/signal.c:1312 [inline]
 group_send_sig_info+0x1fa/0x260 kernel/signal.c:1462
 do_bpf_send_signal+0x7f/0x190 kernel/trace/bpf_trace.c:836
 irq_work_single+0xd5/0x230 kernel/irq_work.c:221
 irq_work_run_list kernel/irq_work.c:252 [inline]
 irq_work_run+0x156/0x2e0 kernel/irq_work.c:261
 __sysvec_irq_work+0x98/0x380 arch/x86/kernel/irq_work.c:22
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x9c/0xc0 arch/x86/kernel/irq_work.c:17
 </IRQ>
 <TASK>
 asm_sysvec_irq_work+0x1a/0x20 arch/x86/include/asm/idtentry.h:723
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x39/0x50 arch/x86/include/asm/apic.h:196
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 f3 0f 1e fa 89 f6 31 d2 e9 f7 36 19 03 0f 1f 80 00 00 00
RSP: 0018:ffffc90003887cd8 EFLAGS: 00000246
RAX: 00000000000000f6 RBX: 0000000000000200 RCX: 000000000000083f
RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000083f
RBP: 0000000000000000 R08: ffffc90003887c47 R09: 1ffff92000710f88
R10: dffffc0000000000 R11: fffff52000710f89 R12: ffff8880b8e35001
R13: dffffc0000000000 R14: ffff8880b8e35050 R15: 0000000000000020
 __apic_send_IPI_self arch/x86/include/asm/apic.h:454 [inline]
 arch_irq_work_raise+0x68/0x70 arch/x86/kernel/irq_work.c:31
 irq_work_queue+0x99/0x140 kernel/irq_work.c:124
 bpf_send_signal_common+0x2b6/0x420 kernel/trace/bpf_trace.c:875
 ____bpf_send_signal kernel/trace/bpf_trace.c:884 [inline]
 bpf_send_signal+0x19/0x20 kernel/trace/bpf_trace.c:882
 bpf_prog_7ba5217f62dcd359+0x40/0x44
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:612 [inline]
 bpf_prog_run include/linux/filter.h:619 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
 bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
 trace_sys_enter+0x69/0x80 include/trace/events/syscalls.h:18
 syscall_trace_enter+0xf0/0x150 kernel/entry/common.c:81
 do_syscall_64+0x28/0xb0 arch/x86/entry/common.c:77
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6d7232b829
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007f6d705b3b40 EFLAGS: 00000246 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 00007f6d725e6188 RCX: 00007f6d7232b829
RDX: 00007f6d705b3b40 RSI: 00007f6d705b3c70 RDI: 0000000000000011
RBP: 00007f6d725e6180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6d725e6218 R14: 00007ffff56aa5a0 R15: 00007ffff56aa688
 </TASK>
sched: RT throttling activated

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/19 04:54 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_mmap
2025/12/12 12:57 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in kcov_mmap
2025/11/25 09:57 linux-6.6.y 1e89a1be4fe9 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in kcov_mmap
* Struck through repros no longer work on HEAD.