INFO: rcu detected stall in kernfs_fop_write_iter (3)

Status: upstream: reported C repro on 2026/01/07 17:45
Subsystems: net
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+10b515098afdcfc455c7@syzkaller.appspotmail.com
First crash: 328d, last: 6d07h
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
603593ca assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: rcu detected stall in kernfs_fop_write_iter (3) 2026/05/21 19:54 2026/05/21 19:54 2026/05/21 20:57 d5742584
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] INFO: rcu detected stall in kernfs_fop_write_iter (3) 0 (2) 2026/08/30 00:30
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in kernfs_fop_write_iter (2) net mm 1 4 498d 659d 0/29 auto-obsoleted due to no activity on 2025/07/23 14:56
linux-6.1 INFO: rcu detected stall in kernfs_fop_write_iter (4) 1 2 179d 247d 0/3 auto-obsoleted due to no activity on 2026/06/17 16:43
linux-5.15 INFO: rcu detected stall in kernfs_fop_write_iter 1 1 676d 676d 0/3 auto-obsoleted due to no activity on 2025/02/05 10:26
linux-6.1 INFO: rcu detected stall in kernfs_fop_write_iter (2) 1 2 760d 857d 0/3 auto-obsoleted due to no activity on 2024/11/14 04:13
linux-6.1 INFO: rcu detected stall in kernfs_fop_write_iter (3) 1 1 359d 359d 0/3 auto-obsoleted due to no activity on 2025/12/19 09:23
linux-5.15 INFO: rcu detected stall in kernfs_fop_write_iter (2) 1 2 24d 124d 0/3 upstream: reported on 2026/05/04 00:10
upstream INFO: rcu detected stall in kernfs_fop_write_iter fs sctp 1 7 753d 848d 0/29 auto-obsoleted due to no activity on 2024/11/10 20:48
linux-6.1 INFO: rcu detected stall in kernfs_fop_write_iter 1 1 1136d 1136d 0/3 auto-obsoleted due to no activity on 2023/11/03 22:13
android-6-1 BUG: soft lockup in kernfs_fop_write_iter 1 1 480d 480d 0/2 auto-obsoleted due to no activity on 2025/08/11 05:47
Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/08/15 04:30 28m retest repro upstream report job log log
2026/07/25 17:57 2h02m retest repro upstream log
2026/06/04 04:47 25m retest repro upstream log
2026/04/25 10:19 28m retest repro upstream report log
2026/04/19 06:19 37m retest repro linux-next no crash log
2026/04/19 06:19 40m retest repro linux-next no crash log
2026/04/19 05:28 43m retest repro linux-next no crash log
2026/04/19 05:28 31m retest repro linux-next no crash log
2026/02/13 18:10 53m retest repro upstream report log
2026/02/13 18:10 44m retest repro upstream report log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 ticks this GP) idle=51bc/1/0x4000000000000000 softirq=17926/17938 fqs=6
rcu: 	(detected by 0, t=10502 jiffies, g=16769, q=4471 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 4984 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:check_preemption_disabled+0x1a/0xd0 lib/smp_processor_id.c:53
Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41 57 41 56 53 65 8b 05 4b ee b0 07 65 48 8b 0d 1b ee b0 07 85 c9 74 0c 5b <41> 5e 41 5f 5d c3 cc cc cc cc cc 9c 59 f7 c1 00 02 00 00 74 ea 65
RSP: 0018:ffffc90000a18d68 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 00000000ffffffff RCX: 0000000001000001
RDX: 0000000001000001 RSI: ffffffff8e48da65 RDI: ffffffff8c6d8b80
RBP: 00000000ffffffff R08: 0000000001000001 R09: 0000000000000000
R10: ffff88802b880308 R11: ffffed1005710063 R12: 0000000000000046
R13: ffff88807ed40000 R14: ffff8880b8728298 R15: ffff8880b8728390
FS:  00007f352db77880(0000) GS:ffff888124de0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556bd98a38 CR3: 000000007efac000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lockdep_recursion_inc kernel/locking/lockdep.c:465 [inline]
 lock_is_held_type+0x5a/0x150 kernel/locking/lockdep.c:5981
 lock_is_held include/linux/lockdep.h:249 [inline]
 __run_hrtimer kernel/time/hrtimer.c:2033 [inline]
 __hrtimer_run_queues+0x20b/0xa10 kernel/time/hrtimer.c:2124
 hrtimer_interrupt+0x4cd/0xaa0 kernel/time/hrtimer.c:2243
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:add_uevent_var+0x25f/0x460 lib/kobject_uevent.c:692
Code: 01 00 00 e8 63 ee ed f5 4c 8b 64 24 38 42 0f b6 04 3b 84 c0 48 8b 54 24 10 0f 85 aa 01 00 00 49 83 c4 18 4c 63 32 41 8d 46 01 <89> 02 bf 40 00 00 00 44 89 f6 e8 32 f3 ed f5 49 83 fe 3f 0f 87 aa
RSP: 0018:ffffc9000253f880 EFLAGS: 00000286
RAX: 0000000000000009 RBX: 1ffff1100feb9043 RCX: ffff88807ed40000
RDX: ffff88807f5c8218 RSI: 000000000000007b RDI: 0000000000000801
RBP: ffffc9000253f9b0 R08: ffffc9000253f757 R09: 0000000000000000
R10: ffffc9000253f740 R11: fffff520004a7eeb R12: ffff88807f5c8018
R13: 1ffff920004a7f20 R14: 0000000000000008 R15: dffffc0000000000
 dev_uevent+0x4ab/0x870 drivers/base/core.c:2774
 kobject_uevent_env+0x475/0x9e0 lib/kobject_uevent.c:576
 kobject_synth_uevent+0x45e/0x950 lib/kobject_uevent.c:207
 uevent_store+0x26/0x70 drivers/base/core.c:2847
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f352d4a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff3d25d8b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f352db77880 RCX: 00007f352d4a7407
RDX: 0000000000000007 RSI: 000055716b1e2a00 RDI: 000000000000000c
RBP: 000055716b1e2a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000007
R13: 000055716b1ea8a0 R14: 00007f352d5efea0 R15: 00007fff3d25dbf0
 </TASK>
rcu: rcu_preempt kthread starved for 10472 jiffies! g16769 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->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:27496 pid:17    tgid:17    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 __schedule_loop kernel/sched/core.c:7347 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7362
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 5760 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:csd_lock_wait kernel/smp.c:363 [inline]
RIP: 0010:csd_lock kernel/smp.c:396 [inline]
RIP: 0010:smp_call_function_many_cond+0x61e/0x1500 kernel/smp.c:944
Code: b6 04 04 84 c0 0f 85 d5 03 00 00 44 8b 3b 44 89 fe 83 e6 01 31 ff e8 51 51 0c 00 41 83 e7 01 75 07 e8 46 4c 0c 00 eb 3f f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 0f f7 03 01
RSP: 0018:ffffc9000355f420 EFLAGS: 00000293
RAX: ffffffff81bb677e RBX: ffff8880b87414c8 RCX: ffff888020330000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000355f570 R08: ffff88802033159f R09: 1ffff110040662b3
R10: dffffc0000000000 R11: 0000000000000000 R12: 1ffff110170e8299
R13: 0000000000000001 R14: ffff8880b87414c0 R15: 0000000000000001
FS:  000055556bd7d500(0000) GS:ffff888124ce0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe76eb556c8 CR3: 000000007b140000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
 flush_tlb_mm_range+0x8ff/0x1090 arch/x86/mm/tlb.c:1435
 dup_mmap+0x1758/0x1dc0 mm/mmap.c:1884
 dup_mm kernel/fork.c:1543 [inline]
 copy_mm+0x11a/0x480 kernel/fork.c:1595
 copy_process+0x1e75/0x43e0 kernel/fork.c:2307
 kernel_clone+0x2d7/0x940 kernel/fork.c:2766
 __do_sys_clone kernel/fork.c:2908 [inline]
 __se_sys_clone kernel/fork.c:2892 [inline]
 __x64_sys_clone+0x1b6/0x230 kernel/fork.c:2892
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe76ddc6bd2
Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffc068b1d70 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffc068b1d70 RCX: 00007fe76ddc6bd2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc068b1efc R08: 0000000000000000 R09: 0000000000000000
R10: 000055556bd7d7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 000055556bd90a00 R14: 000000000001ae67 R15: 00007ffc068b1f50
 </TASK>

Crashes (27):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/30 00:30 net-next 1b78070aaef6 2f52988a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/16 12:52 upstream 603c05a1639f d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/10 22:31 upstream b6151c4e60e5 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/08/22 13:22 upstream 26260251022f 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/07/04 01:59 upstream d2c9a99135da fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/05/21 03:37 upstream df685633c3db 41b8c833 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/05/10 15:02 upstream 1bfaee9d3351 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/04/05 03:35 upstream 3aae9383f42f 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/04/03 20:38 upstream d8a9a4b11a13 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/11 15:31 upstream 0fa27899e014 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/08 00:03 upstream f0b9d8eb98df d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/02 09:01 upstream b69053dd3ffb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/01 20:11 upstream b69053dd3ffb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2025/12/27 09:39 upstream 3f0e9c8cefa9 d1b870e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in kernfs_fop_write_iter
2025/11/27 08:12 upstream 4941a17751c9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in kernfs_fop_write_iter
2025/11/26 23:09 upstream 30f09200cc4a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2025/11/03 12:49 upstream 6146a0f1dfae 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in kernfs_fop_write_iter
2025/10/11 23:13 upstream 0739473694c4 ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/07/11 08:13 net 1cd23ca80784 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/13 23:27 linux-next 0f853ca2a798 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/05 22:03 linux-next f8f97927abf7 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/04 23:33 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/04 08:26 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/01/03 17:37 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2025/12/16 14:51 linux-next 4a5663c04bb6 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kernfs_fop_write_iter
2026/08/17 08:21 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 21d6ac051080 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 INFO: rcu detected stall in kernfs_fop_write_iter
2026/06/22 06:37 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 92e3f6ef4ffb 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: soft lockup in kernfs_fop_write_iter
* Struck through repros no longer work on HEAD.