INFO: rcu detected stall in chrdev_open (2)

Status: upstream: reported on 2026/05/04 04:53
Reported-by: syzbot+8134f525d5bd4936c0d9@syzkaller.appspotmail.com
First crash: 91d, last: 36d
▶ ▼ Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 INFO: rcu detected stall in chrdev_open (2) 1 1 2270d 2270d 0/1 auto-closed as invalid on 2020/09/12 23:19
upstream INFO: rcu detected stall in chrdev_open (6) mm usb 1 16 581d 848d 0/29 auto-obsoleted due to no activity on 2025/03/29 19:07
linux-6.1 INFO: rcu detected stall in chrdev_open 1 1 240d 240d 0/3 auto-obsoleted due to no activity on 2026/03/15 21:38
linux-5.15 INFO: rcu detected stall in chrdev_open 1 1 316d 316d 0/3 auto-obsoleted due to no activity on 2025/12/29 22:52
linux-4.14 INFO: rcu detected stall in chrdev_open 1 syz, C error 4 1580d 1686d 0/1 upstream: reported C repro on 2021/12/21 07:54
linux-4.19 INFO: rcu detected stall in chrdev_open (3) 1 syz, C error 17 1405d 1959d 0/1 upstream: reported C repro on 2021/03/22 19:09
upstream INFO: rcu detected stall in chrdev_open (3) kernel 1 1 1344d 1344d 0/29 auto-obsoleted due to no activity on 2023/02/09 20:53
upstream INFO: rcu detected stall in chrdev_open (5) serial 1 1 1017d 1017d 0/29 auto-obsoleted due to no activity on 2024/01/19 06:34
linux-4.19 INFO: rcu detected stall in chrdev_open 1 1 2404d 2404d 0/1 auto-closed as invalid on 2020/05/02 02:53
upstream INFO: rcu detected stall in chrdev_open (4) media 1 1 1119d 1119d 0/29 auto-obsoleted due to no activity on 2023/10/08 11:46
upstream INFO: rcu detected stall in chrdev_open (2) serial 1 syz, C done inconclusive 55 1658d 2425d 0/29 closed as invalid on 2022/02/08 10:45
upstream INFO: rcu detected stall in chrdev_open mm 1 4 2434d 2435d 0/29 closed as invalid on 2019/12/04 14:04
linux-5.15 BUG: soft lockup in chrdev_open 1 1 1000d 1000d 0/3 auto-obsoleted due to no activity on 2024/02/14 17:22
android-5-15 BUG: soft lockup in chrdev_open 1 1 764d 764d 0/2 auto-obsoleted due to no activity on 2024/09/28 04:58

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2675 jiffies s: 1133 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4415 Comm: syz.4.5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:perf_output_begin_forward+0x7f/0xa70 kernel/events/ring_buffer.c:271
Code: 7c e0 58 8c 48 c7 84 24 90 00 00 00 60 82 a8 81 4c 8d a4 24 80 00 00 00 49 c1 ec 03 48 b8 f1 f1 f1 f1 f8 f8 f8 f3 4b 89 04 3c <43> c7 44 3c 08 f3 f3 f3 f3 e8 23 9e d9 ff 66 43 c7 44 3c 04 00 00
RSP: 0018:ffffc90000007160 EFLAGS: 00000806
RAX: f3f8f8f8f1f1f1f1 RBX: ffff88801773b000 RCX: 0000000000000010
RDX: ffff88801773b000 RSI: ffffc90000007580 RDI: ffffc900000072e0
RBP: ffffc90000007290 R08: ffffc90000007317 R09: ffffc900000072e0
R10: dffffc0000000000 R11: fffff52000000e63 R12: 1ffff92000000e3c
R13: ffffc900000072e0 R14: 0000000000000010 R15: dffffc0000000000
FS:  00007f2c0aef56c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2c09fea540 CR3: 0000000077d01000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __perf_event_output kernel/events/core.c:7732 [inline]
 perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x457/0x630 kernel/events/core.c:9496
 perf_swevent_overflow kernel/events/core.c:9579 [inline]
 perf_swevent_event+0x315/0x570 kernel/events/core.c:9630
 perf_tp_event+0x36b/0xc10 kernel/events/core.c:10064
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10032
 perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 e2 82 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900000079c0 EFLAGS: 00000206
RAX: 3786196c069d8d00 RBX: 1ffff92000000f40 RCX: 3786196c069d8d00
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adee1a0
RBP: ffffc90000007ab8 R08: ffffffff90af2277 R09: 1ffffffff215e44e
R10: dffffc0000000000 R11: fffffbfff215e44f R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3bb00 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 percpu_ref_put_many include/linux/percpu-refcount.h:337 [inline]
 percpu_ref_put+0xc8/0x100 include/linux/percpu-refcount.h:351
 obj_cgroup_put include/linux/memcontrol.h:795 [inline]
 memcg_slab_free_hook+0x16f/0x200 mm/slab.h:572
 slab_free mm/slub.c:3682 [inline]
 kmem_cache_free+0xe0/0x2a0 mm/slub.c:3709
 rcu_do_batch kernel/rcu/tree.c:2297 [inline]
 rcu_core+0x9a3/0x1740 kernel/rcu/tree.c:2557
 handle_softirqs+0x291/0x910 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:cmpxchg_double_slab+0x128/0x350 mm/slub.c:552
Code: 02 00 00 0f 84 8e 00 00 00 fb e9 88 00 00 00 41 8d 46 20 a8 0f 0f 85 1e 01 00 00 4c 89 c9 4c 89 fa 4c 89 e0 f0 49 0f c7 4e 20 <b0> 01 75 65 eb 67 49 8b 46 08 a8 01 0f 85 e0 01 00 00 0f 1f 44 00
RSP: 0018:ffffc900046e7508 EFLAGS: 00000246
RAX: ffff88807ad63a00 RBX: ffff88807ad63600 RCX: 000000008010000e
RDX: 000000008010000f RSI: ffffea0001eb5880 RDI: ffff8880174c5000
RBP: 0000000000000000 R08: ffff88807ad63600 R09: 000000008010000e
R10: dffffc0000000000 R11: fffffbfff215e44f R12: ffff88807ad63a00
R13: 000000008010000e R14: ffffea0001eb5880 R15: 000000008010000f
 __slab_free+0xa1/0x290 mm/slub.c:3546
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 __kmem_cache_alloc_node+0x19d/0x270 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa3/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:2057
 sk_alloc+0x36/0x330 net/core/sock.c:2113
 tun_chr_open+0x75/0x4d0 drivers/net/tun.c:3459
 misc_open+0x31f/0x390 drivers/char/misc.c:145
 chrdev_open+0x585/0x5f0 fs/char_dev.c:414
 do_dentry_open+0x7dd/0x10b0 fs/open.c:882
 do_open fs/namei.c:3634 [inline]
 path_openat+0x2674/0x2f10 fs/namei.c:3791
 do_filp_open+0x1ee/0x420 fs/namei.c:3818
 do_sys_openat2+0x14b/0x4f0 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f2c09f9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2c0aef5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2c0a215fa0 RCX: 00007f2c09f9ce59
RDX: 0000000000000880 RSI: 0000200000000140 RDI: ffffffffffffff9c
RBP: 00007f2c0a032e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c0a216038 R14: 00007f2c0a215fa0 R15: 00007fffeb4d7908
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/27 14:54 linux-6.1.y fdb6fcb41cc7 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in chrdev_open
2026/05/04 04:52 linux-6.1.y 4931e0e1673d a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in chrdev_open
* Struck through repros no longer work on HEAD.