syzbot

 sign-in | mailing list | source | docs | 🏰
🐞 Open [1321]
≡ Subsystems
🐞 Fixed [7197]
🐞 Invalid [19022]
⬇ Missing Backports [221]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
Total Repo Heatmap Subsystems Heatmap
✨ AI
💬 Send us feedback

INFO: rcu detected stall in ppp_ioctl

Status: auto-obsoleted due to no activity on 2025/02/10 18:41
Subsystems: mm
[Documentation on labels]
First crash: 610d, last: 596d
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in ppp_ioctl (3) 1 1 60d 60d 0/3 upstream: reported on 2026/05/01 22:48
linux-5.15 INFO: rcu detected stall in ppp_ioctl 1 1 189d 189d 0/3 auto-obsoleted due to no activity on 2026/04/02 20:21
linux-6.1 INFO: rcu detected stall in ppp_ioctl 1 1 638d 638d 0/3 auto-obsoleted due to no activity on 2025/01/09 16:14
linux-6.1 INFO: rcu detected stall in ppp_ioctl (2) 1 1 258d 258d 0/3 auto-obsoleted due to no activity on 2026/01/24 16:32
linux-6.6 INFO: rcu detected stall in ppp_ioctl 1 1 10d 10d 0/2 upstream: reported on 2026/06/20 19:57
android-5-15 BUG: soft lockup in ppp_ioctl 1 5 675d 802d 0/2 auto-obsoleted due to no activity on 2024/11/22 22:02

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10017/1:b..l P5868/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=41549, q=829 ncpus=2)
task:syz-executor    state:R  running task     stack:18928 pid:5868  tgid:5868  ppid:5843   flags:0x00000002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x18af/0x4bd0 kernel/sched/core.c:6690
 preempt_schedule_common+0x84/0xd0 kernel/sched/core.c:6869
 preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6893
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk.S:12
 unwind_next_frame+0x18f8/0x22d0 arch/x86/kernel/unwind_orc.c:672
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x118/0x1d0 kernel/stacktrace.c:122
 save_stack+0xfb/0x1f0 mm/page_owner.c:156
 __reset_page_owner+0x76/0x430 mm/page_owner.c:297
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1108 [inline]
 free_unref_page+0xcfb/0xf20 mm/page_alloc.c:2638
 discard_slab mm/slub.c:2677 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:3145
 put_cpu_partial+0x17c/0x250 mm/slub.c:3220
 __slab_free+0x2ea/0x3d0 mm/slub.c:4449
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:247 [inline]
 slab_post_alloc_hook mm/slub.c:4085 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4141
 getname_flags+0xb7/0x540 fs/namei.c:139
 getname fs/namei.c:225 [inline]
 __do_sys_unlink fs/namei.c:4581 [inline]
 __se_sys_unlink fs/namei.c:4579 [inline]
 __x64_sys_unlink+0x3a/0x50 fs/namei.c:4579
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff11b17dcc7
RSP: 002b:00007ff11b45ecc8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff11b17dcc7
RDX: 00007ff11b45ecf0 RSI: 00007ff11b45ed80 RDI: 00007ff11b45ed80
RBP: 00007ff11b45ed80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ff11b45fe00
R13: 00007ff11b1f11cc R14: 000000000003d9d5 R15: 00007ff11b45fe40
 </TASK>
task:syz.2.697       state:R  running task     stack:22608 pid:10017 tgid:10015 ppid:9366   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x18af/0x4bd0 kernel/sched/core.c:6690
 preempt_schedule_irq+0xfb/0x1c0 kernel/sched/core.c:7012
 irqentry_exit+0x5e/0x90 kernel/entry/common.c:354
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__preempt_count_add arch/x86/include/asm/preempt.h:79 [inline]
RIP: 0010:rcu_is_watching+0x9/0xb0 kernel/rcu/tree.c:736
Code: 03 eb cd 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 41 56 53 <65> ff 05 e8 11 89 7e e8 3b 3f 4c 0a 89 c3 83 f8 08 73 7a 49 bf 00
RSP: 0018:ffffc9000b61f488 EFLAGS: 00000202
RAX: 0000000000000002 RBX: 0000000000000001 RCX: ffff888025451e00
RDX: ffff888025451e00 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff820b6726 R09: 1ffff11003d072c3
R10: dffffc0000000000 R11: ffffed1003d072c4 R12: 0000000000000000
R13: ffffea0001c2de48 R14: 1ffffd4000385bc9 R15: 1ffffd4000385bc8
 rcu_read_unlock include/linux/rcupdate.h:878 [inline]
 page_ext_put+0x2f/0xc0 mm/page_ext.c:550
 page_table_check_free include/linux/page_table_check.h:41 [inline]
 free_pages_prepare mm/page_alloc.c:1109 [inline]
 free_unref_page+0xd0f/0xf20 mm/page_alloc.c:2638
 discard_slab mm/slub.c:2677 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:3145
 put_cpu_partial+0x17c/0x250 mm/slub.c:3220
 __slab_free+0x2ea/0x3d0 mm/slub.c:4449
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:247 [inline]
 slab_post_alloc_hook mm/slub.c:4085 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4141
 __kernfs_new_node+0xd8/0x870 fs/kernfs/dir.c:624
 kernfs_new_node+0x137/0x240 fs/kernfs/dir.c:700
 __kernfs_create_file+0x49/0x2e0 fs/kernfs/file.c:1034
 sysfs_add_file_mode_ns+0x24a/0x310 fs/sysfs/file.c:307
 sysfs_merge_group+0x1fd/0x450 fs/sysfs/group.c:373
 dpm_sysfs_add+0xd3/0x280 drivers/base/power/sysfs.c:707
 device_add+0x5bc/0xbf0 drivers/base/core.c:3635
 netdev_register_kobject+0x17e/0x310 net/core/net-sysfs.c:2139
 register_netdevice+0x12c5/0x1b00 net/core/dev.c:10491
 ppp_unit_register drivers/net/ppp/ppp_generic.c:1219 [inline]
 ppp_dev_configure+0x883/0xb10 drivers/net/ppp/ppp_generic.c:1275
 ppp_create_interface drivers/net/ppp/ppp_generic.c:3348 [inline]
 ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1060 [inline]
 ppp_ioctl+0x797/0x1cd0 drivers/net/ppp/ppp_generic.c:733
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe9a317e719
RSP: 002b:00007fe9a2bff038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe9a3335f80 RCX: 00007fe9a317e719
RDX: 00000000200000c0 RSI: 00000000c004743e RDI: 0000000000000008
RBP: 00007fe9a31f132e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe9a3335f80 R15: 00007fe9a345fa28
 </TASK>
rcu: rcu_preempt kthread starved for 10480 jiffies! g41549 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:26112 pid:17    tgid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x18af/0x4bd0 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6782
 schedule_timeout+0x1be/0x310 kernel/time/timer.c:2615
 rcu_gp_fqs_loop+0x2df/0x1330 kernel/rcu/tree.c:2045
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:2247
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
Code: 9c 8f 44 24 20 42 80 3c 23 00 74 08 4c 89 f7 e8 0e f0 2d f6 f6 44 24 21 02 75 52 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 93 88 92 f5 65 8b 05 64 32 33 74 85 c0 74 43 48 c7 04 24 0e 36
RSP: 0018:ffffc90000157160 EFLAGS: 00000206
RAX: c56911433a1dce00 RBX: 1ffff9200002ae30 RCX: ffffffff8170be1a
RDX: dffffc0000000000 RSI: ffffffff8c0acaa0 RDI: 0000000000000001
RBP: ffffc90000157200 R08: ffffffff942ca91f R09: 1ffffffff2859523
R10: dffffc0000000000 R11: fffffbfff2859524 R12: dffffc0000000000
R13: 1ffff9200002ae2c R14: ffffc90000157180 R15: 0000000000000246
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff11b45ecdc CR3: 000000002e272000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 </IRQ>
 <TASK>
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 backlog_unlock_irq_restore net/core/dev.c:250 [inline]
 enqueue_to_backlog+0x8b2/0xc80 net/core/dev.c:4887
 netif_rx_internal+0x17a/0x630 net/core/dev.c:5195
 netif_rx+0x59/0x90 net/core/dev.c:5248
 vxcan_xmit+0x482/0x760 drivers/net/can/vxcan.c:73
 __netdev_start_xmit include/linux/netdevice.h:4928 [inline]
 netdev_start_xmit include/linux/netdevice.h:4937 [inline]
 xmit_one net/core/dev.c:3588 [inline]
 dev_hard_start_xmit+0x27a/0x7e0 net/core/dev.c:3604
 __dev_queue_xmit+0x1b11/0x3ed0 net/core/dev.c:4428
 dev_queue_xmit include/linux/netdevice.h:3094 [inline]
 can_send+0x8b3/0xcd0 net/can/af_can.c:276
 bcm_can_tx+0x5dd/0x9a0 net/can/bcm.c:314
 bcm_tx_timeout_handler+0x182/0x520
 __run_hrtimer kernel/time/hrtimer.c:1691 [inline]
 __hrtimer_run_queues+0x59b/0xd50 kernel/time/hrtimer.c:1755
 hrtimer_run_softirq+0x19a/0x2c0 kernel/time/hrtimer.c:1772
 handle_softirqs+0x2c5/0x980 kernel/softirq.c:554
 run_ksoftirqd+0xca/0x130 kernel/softirq.c:927
 smpboot_thread_fn+0x544/0xa30 kernel/smpboot.c:164
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/10/29 02:55 upstream 819837584309 9efb3cc7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in ppp_ioctl
2024/11/12 18:34 net-next a58f00ed24b8 75bb1b32 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in ppp_ioctl
2024/11/02 00:34 net-next dbb9a7ef3478 f00eed24 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in ppp_ioctl
* Struck through repros no longer work on HEAD.