syzbot

 sign-in | mailing list | source | docs
🐞 Open [896]
🐞 Fixed [141]
🐞 Invalid [1049]
⬇ Missing Backports [73]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in syscall_enter_from_user_mode (3)

Status: upstream: reported C repro on 2025/02/27 13:22
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+d27661ce10e475e27efe@syzkaller.appspotmail.com
First crash: 393d, last: 5d23h
Fix commit to backport (bisect log) :
tree: upstream
commit f4bf3ca2e5cba655824b6e0893a98dfb33ed24e5
Author: Lingutla Chandrasekhar <clingutla@codeaurora.org>
Date: Fri Apr 7 23:05:26 2023 +0000

  softirq: Add trace points for tasklet entry/exit

  
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: no output from test machine (log)
Repro: syz .config
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/08/27 linux-6.1.y (ToT) 0bc96de781b4 C [report] INFO: rcu detected stall in perf_event_open
2025/08/27 upstream (ToT) 39f90c196721 C Didn't crash
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode (2) 1 1 599d 599d 0/3 auto-obsoleted due to no activity on 2024/11/13 07:03
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 996d 996d 0/3 auto-obsoleted due to no activity on 2023/10/13 06:46
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (2) kernel 1 11 1172d 1461d 0/29 auto-obsoleted due to no activity on 2023/04/22 11:15
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (3) kernel 1 5 836d 1001d 0/29 auto-obsoleted due to no activity on 2024/03/11 14:48
linux-5.15 INFO: rcu detected stall in syscall_enter_from_user_mode missing-backport origin:upstream 1 C done 141 1d06h 835d 0/3 upstream: reported C repro on 2023/12/13 03:22
linux-6.6 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 136d 136d 0/2 auto-obsoleted due to no activity on 2026/02/19 17:17
upstream INFO: rcu detected stall in syscall_enter_from_user_mode kernel 1 2 1518d 1532d 0/29 closed as invalid on 2022/02/08 10:10
android-5-15 BUG: soft lockup in syscall_enter_from_user_mode 1 1 680d 680d 0/2 auto-obsoleted due to no activity on 2024/08/14 14:14
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2025/11/13 01:20 11h02m fix candidate upstream OK (1) job log
2025/06/27 04:15 2h09m fix candidate upstream OK (0) job log
2025/06/06 18:47 2h16m bisect fix linux-6.1.y OK (0) job log log
2025/04/07 14:34 2h31m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2679 jiffies s: 3353 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: 4526 Comm: syz.2.64 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:lock_is_held_type+0x0/0x190 kernel/locking/lockdep.c:5690
Code: 04 f3 03 00 75 d6 48 c7 c7 c0 10 8c 8a 48 c7 c6 00 11 8c 8a e8 f1 db 20 f7 0f 0b eb bf e8 98 fd ff ff 0f 1f 84 00 00 00 00 00 <55> 41 57 41 56 41 55 41 54 53 48 83 ec 10 65 48 8b 04 25 28 00 00
RSP: 0018:ffffc90000007438 EFLAGS: 00000002
RAX: 1ffffffff1966501 RBX: 0000000000000001 RCX: 2f14f06eb5be4300
RDX: ffff888075385940 RSI: 00000000ffffffff RDI: ffffffff8cb2d620
RBP: ffffc90000007538 R08: dffffc0000000000 R09: 1ffffffff215ec48
R10: dffffc0000000000 R11: fffffbfff215ec49 R12: ffffffff8cb7fca0
R13: 1ffff92000000e94 R14: ffff88807e565b00 R15: 0000000000000000
FS:  0000555587b29500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1713be8000 CR3: 000000002ede7000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 trace_call_bpf+0x19e/0x6b0 kernel/trace/bpf_trace.c:135
 perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:9997
 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 33 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:ffffc90000007760 EFLAGS: 00000206
RAX: 2f14f06eb5be4300 RBX: 1ffff92000000ef4 RCX: 2f14f06eb5be4300
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0f60
RBP: ffffc90000007860 R08: ffffffff90af634f R09: 1ffffffff215ec69
R10: dffffc0000000000 R11: fffffbfff215ec6a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ndisc_send_skb+0xd9d/0x14e0 net/ipv6/ndisc.c:521
 addrconf_rs_timer+0x2d1/0x630 net/ipv6/addrconf.c:3979
 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:2023
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x2a1/0x930 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:__syscall_enter_from_user_work kernel/entry/common.c:97 [inline]
RIP: 0010:syscall_enter_from_user_mode+0x2a/0x80 kernel/entry/common.c:118
Code: 41 56 53 48 89 f3 49 89 fe 48 8b 7c 24 10 e8 ed fa ff ff 66 90 66 90 e8 34 d1 5b f7 e8 af cf 5b f7 fb 65 48 8b 05 36 63 d5 75 <48> 8b 70 08 40 f6 c6 3f 74 0b 4c 89 f7 5b 41 5e e9 41 2f 42 f7 48
RSP: 0018:ffffc9000357ff08 EFLAGS: 00000286
RAX: ffff888075385940 RBX: 00000000000000ca RCX: 2f14f06eb5be4300
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0f60
RBP: ffffc9000357ff48 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000000
R13: 0000000000000000 R14: ffffc9000357ff58 R15: 0000000000000000
 do_syscall_64+0x24/0xa0 arch/x86/entry/common.c:72
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f633839c799
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:00007fff9a3b8c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f633839c799
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f6338615fa8
RBP: 0000000000000092 R08: 0000000000000002 R09: 0000000000000000
R10: 00007f6338615fa0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6338615fac R14: 00007f6338615fa8 R15: 00007f6338615fa0
 </TASK>

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/21 21:33 linux-6.1.y f2ddafa93a25 5b92003d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/29 05:36 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/08/20 21:50 linux-6.1.y 0bc96de781b4 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/01/18 00:54 linux-6.1.y cd9b81672742 20d37d28 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/10/16 18:59 linux-6.1.y c2fda4b3f577 19568248 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/02/27 13:21 linux-6.1.y 3a8358583626 6a8fcbc4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/02/19 02:49 linux-6.1.y 8ce36b2849ef 77d4d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/01/30 06:19 linux-6.1.y cd9b81672742 bfa73b7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/15 11:47 linux-6.1.y f6e38ae624cf f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/11 14:28 linux-6.1.y f6e38ae624cf 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/09/21 21:32 linux-6.1.y 363a599da6d9 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/08/15 07:02 linux-6.1.y 3594f306da12 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in syscall_enter_from_user_mode
* Struck through repros no longer work on HEAD.