syzbot

 sign-in | mailing list | source | docs
🐞 Open [926]
🐞 Fixed [144]
🐞 Invalid [1145]
⬇ Missing Backports [73]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in __fput

Status: upstream: reported on 2026/06/14 03:02
Reported-by: syzbot+31fd09a6f69d194fabaa@syzkaller.appspotmail.com
First crash: 9d20h, last: 6d03h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __fput (3) fs 1 1 452d 452d 0/29 auto-obsoleted due to no activity on 2025/06/26 03:51
linux-5.15 INFO: rcu detected stall in __fput origin:lts-only 1 C error 1 74d 74d 0/3 upstream: reported C repro on 2026/04/10 20:21
upstream INFO: rcu detected stall in __fput (2) fs 1 3 605d 634d 0/29 auto-obsoleted due to no activity on 2025/01/24 10:50
upstream INFO: rcu detected stall in __fput fs 1 1 1766d 1766d 0/29 auto-closed as invalid on 2021/10/21 19:09

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P5574 0-.... } 2665 jiffies s: 8113 root: 0x1/T
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5574 Comm: syz.1.361 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:85 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x84/0x290 mm/kasan/generic.c:189
Code: 49 c1 e9 03 4b 8d 1c 21 49 89 df 4d 29 df 49 83 ff 10 7f 29 4d 85 ff 0f 84 38 01 00 00 4c 89 cb 48 f7 d3 4c 01 f3 41 80 3b 00 <0f> 85 86 01 00 00 49 ff c3 48 ff c3 75 ee e9 18 01 00 00 44 89 dd
RSP: 0018:ffffc900000070d0 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffffffffffffffff RCX: ffffffff8164c380
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e2029e8
RBP: ffffc90000007210 R08: ffffffff8e2029ef R09: 1ffffffff1c4053d
R10: dffffc0000000000 R11: fffffbfff1c4053d R12: dffffc0000000001
R13: dffffc0000000000 R14: 1ffffffff1c4053d R15: 0000000000000001
FS:  00007f173d3316c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000555fb000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 cpumask_test_cpu include/linux/cpumask.h:444 [inline]
 cpu_online include/linux/cpumask.h:1030 [inline]
 trace_lock_release include/trace/events/lock.h:69 [inline]
 lock_release+0xc0/0x920 kernel/locking/lockdep.c:5673
 rcu_lock_release include/linux/rcupdate.h:355 [inline]
 rcu_read_unlock include/linux/rcupdate.h:824 [inline]
 __perf_event_output kernel/events/core.c:7741 [inline]
 perf_event_output_forward+0x282/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x448/0x610 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+0x3e7/0xc30 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 82 30 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:ffffc90000007940 EFLAGS: 00000206
RAX: 3234cdfe2bb04a00 RBX: 1ffff92000000f30 RCX: 3234cdfe2bb04a00
RDX: dffffc0000000000 RSI: ffffffff8a8c1aa0 RDI: ffffffff8adf2060
RBP: ffffc90000007a28 R08: ffffffff90aff24f R09: 1ffffffff215fe49
R10: dffffc0000000000 R11: fffffbfff215fe4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b901 R15: ffff888029ee3c00
 __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+0x16d/0x1f0 mm/slab.h:572
 slab_free mm/slub.c:3682 [inline]
 __kmem_cache_free+0x9f/0x1f0 mm/slub.c:3700
 security_cred_free+0xbc/0xf0 security/security.c:1733
 put_cred_rcu+0xdd/0x3e0 kernel/cred.c:115
 rcu_do_batch kernel/rcu/tree.c:2297 [inline]
 rcu_core+0xa99/0x1740 kernel/rcu/tree.c:2557
 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: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 82 30 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:ffffc90005377c00 EFLAGS: 00000206
RAX: 3234cdfe2bb04a00 RBX: 1ffff92000a6ef88 RCX: 3234cdfe2bb04a00
RDX: dffffc0000000000 RSI: ffffffff8a8c1aa0 RDI: ffffffff8adf2060
RBP: ffffc90005377cf8 R08: ffffffff90aff24f R09: 1ffffffff215fe49
R10: dffffc0000000000 R11: fffffbfff215fe4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b901 R15: ffff888029ee3c00
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock+0x85/0xa0 include/linux/rcupdate.h:823
 dput+0xe2/0x1d0 fs/dcache.c:911
 __fput+0x5e0/0x920 fs/file_table.c:328
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f173c39ce59
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:00007f173d331028 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007f173c615fa0 RCX: 00007f173c39ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f173c432d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f173c616038 R14: 00007f173c615fa0 R15: 00007fffd6879458
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/17 20:05 linux-6.1.y 228da13e907e b62b3ded .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in __fput
2026/06/14 03:01 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in __fput
* Struck through repros no longer work on HEAD.