INFO: rcu detected stall in ppp_ioctl (4)

Status: upstream: reported on 2026/09/19 16:18
Reported-by: syzbot+568f30a2d5f4705b7371@syzkaller.appspotmail.com
First crash: 5d21h, last: 5d21h
▶ ▼ Similar bugs (7)
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 146d 146d 0/3 auto-obsoleted due to no activity on 2026/08/09 22:48
linux-5.15 INFO: rcu detected stall in ppp_ioctl 1 1 275d 275d 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 723d 723d 0/3 auto-obsoleted due to no activity on 2025/01/09 16:14
upstream INFO: rcu detected stall in ppp_ioctl mm 1 3 681d 696d 0/29 auto-obsoleted due to no activity on 2025/02/10 18:41
linux-6.1 INFO: rcu detected stall in ppp_ioctl (2) 1 1 343d 343d 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 96d 96d 0/2 upstream: reported on 2026/06/20 19:57
android-5-15 BUG: soft lockup in ppp_ioctl 1 5 761d 888d 0/2 auto-obsoleted due to no activity on 2024/11/22 22:02

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2637 jiffies s: 45697 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 11766 Comm: syz.1.1680 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:hlock_class kernel/locking/lockdep.c:228 [inline]
RIP: 0010:__lock_acquire+0x1392/0x7c40 kernel/locking/lockdep.c:5060
Code: 03 89 c3 81 e3 ff 1f 00 00 c1 e8 03 25 f8 03 00 00 48 8d b8 40 f2 b0 90 be 08 00 00 00 e8 c6 65 6f 00 48 0f a3 1d ce de 4c 0f <73> 1a 48 8d 04 5b c1 e0 06 48 8d 98 00 71 49 90 49 b8 00 00 00 00
RSP: 0018:ffffc900001e0440 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 000000000000002d RCX: ffffffff8164136a
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90b0f240
RBP: ffffc900001e0670 R08: ffffffff90b0f247 R09: 1ffffffff2161e48
R10: dffffc0000000000 R11: fffffbfff2161e49 R12: ffff88802c5ea8d8
R13: ffff88802c5e9e00 R14: 00000000f5e10535 R15: 0000000094482581
FS:  00007fa67758c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb55e3b1ff8 CR3: 0000000057247000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5678
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 trace_call_bpf+0xe0/0x6b0 kernel/trace/bpf_trace.c:134
 perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10037
 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 32 7b 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:ffffc900001e0ae0 EFLAGS: 00000206
RAX: 47cac08e4b787a00 RBX: 1ffff9200003c164 RCX: 47cac08e4b787a00
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: ffffffff8adf68a0
RBP: ffffc900001e0bd0 R08: ffffffff90b0f24f R09: 1ffffffff2161e49
R10: dffffc0000000000 R11: fffffbfff2161e4a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3bb00 R15: 0000000000000002
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
 mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2148
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
 hrtimer_run_softirq+0x173/0x290 kernel/time/hrtimer.c:1832
 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:kernfs_root fs/kernfs/kernfs-internal.h:68 [inline]
RIP: 0010:kernfs_activate_one+0x79/0x390 fs/kernfs/dir.c:1347
Code: c1 e8 03 42 80 3c 20 00 74 05 e8 c2 0f cc ff 4c 8b 73 30 4d 85 f6 4c 0f 44 f3 49 83 c6 78 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 <74> 08 4c 89 f7 e8 9d 0f cc ff bf 48 01 00 00 49 03 3e 31 f6 e8 ae
RSP: 0018:ffffc900032478c0 EFLAGS: 00000246
RAX: 1ffff1100ae79331 RBX: ffff88802065b9f8 RCX: 0000000000000002
RDX: ffff88802c5e9e00 RSI: 0000000000000001 RDI: ffff88802065ba28
RBP: 0000000000000001 R08: ffff8880174734e7 R09: 1ffff11002e8e69c
R10: dffffc0000000000 R11: ffffed1002e8e69d R12: dffffc0000000000
R13: ffff88802065ba90 R14: ffff8880573c9988 R15: ffff88802065b9f8
 kernfs_activate fs/kernfs/dir.c:1382 [inline]
 kernfs_add_one+0x5dc/0x8f0 fs/kernfs/dir.c:806
 kernfs_create_dir_ns+0xda/0x120 fs/kernfs/dir.c:1056
 internal_create_group+0x21a/0xce0 fs/sysfs/group.c:136
 dpm_sysfs_add+0x66/0x270 drivers/base/power/sysfs.c:702
 device_add+0x745/0x1050 drivers/base/core.c:3654
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2013
 register_netdevice+0x133a/0x1b80 net/core/dev.c:10243
 ppp_unit_register drivers/net/ppp/ppp_generic.c:1224 [inline]
 ppp_dev_configure+0x875/0xad0 drivers/net/ppp/ppp_generic.c:1280
 ppp_create_interface drivers/net/ppp/ppp_generic.c:3378 [inline]
 ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1065 [inline]
 ppp_ioctl+0x8eb/0x1b20 drivers/net/ppp/ppp_generic.c:731
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 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: 0033:0x7fa67679e159
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:00007fa67758c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa676a25fa0 RCX: 00007fa67679e159
RDX: 000000110c230000 RSI: 00000000c004743e RDI: 0000000000000014
RBP: 00007fa67683506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa676a26038 R14: 00007fa676a25fa0 R15: 00007ffc6e34b308
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/19 16:18 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in ppp_ioctl
* Struck through repros no longer work on HEAD.