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INFO: rcu detected stall in ppp_ioctl (3)

Status: upstream: reported on 2026/05/01 22:48
Reported-by: syzbot+319e3b2e98552460a879@syzkaller.appspotmail.com
First crash: 4h04m, last: 4h04m
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in ppp_ioctl 1 1 129d 129d 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 577d 577d 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 535d 549d 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 197d 197d 0/3 auto-obsoleted due to no activity on 2026/01/24 16:32
android-5-15 BUG: soft lockup in ppp_ioctl 1 5 615d 742d 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-.... } 2631 jiffies s: 2917 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: 5113 Comm: syz.2.243 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__kasan_check_read+0x6/0x10 mm/kasan/shadow.c:31
Code: 41 5f 5d c3 48 c7 c7 52 e5 60 8c eb 0a 48 c7 c7 ae 83 45 8c 48 89 de e8 98 2a 4f 08 31 ed eb d7 00 00 cc cc 89 f6 48 8b 0c 24 <31> d2 e9 a3 ec ff ff 0f 1f 00 89 f6 48 8b 0c 24 ba 01 00 00 00 e9
RSP: 0018:ffffc900001e0318 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000003 RCX: ffffffff81644b6a
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90af9240
RBP: ffffc900001e0570 R08: dffffc0000000000 R09: 1ffffffff215f248
R10: dffffc0000000000 R11: fffffbfff215f249 R12: ffff888028c52938
R13: ffff888028c52802 R14: 000000000000002c R15: ffff888028c52938
FS:  00007f937909d6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd450d4da08 CR3: 000000007e188000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 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]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 check_wait_context kernel/locking/lockdep.c:4748 [inline]
 __lock_acquire+0x93a/0x7d10 kernel/locking/lockdep.c:4999
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock_sched include/linux/rcupdate.h:883 [inline]
 pfn_valid include/linux/mmzone.h:1857 [inline]
 __virt_addr_valid+0x1a5/0x540 arch/x86/mm/physaddr.c:65
 kasan_addr_to_slab+0x9/0xc0 mm/kasan/common.c:36
 __kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:471
 irq_work_queue_on+0x10f/0x260 kernel/irq_work.c:140
 rcu_read_unlock_special+0x3c9/0x510 kernel/rcu/tree_plugin.h:678
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 trace_call_bpf+0x5bb/0x6b0 kernel/trace/bpf_trace.c:137
 perf_trace_run_bpf_submit+0x79/0x1c0 kernel/events/core.c:10027
 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+0x34/0xd0 kernel/rcu/tree_plugin.h:423
Code: bf 00 00 00 00 00 fc ff df 65 48 8b 3d f5 34 95 7e 48 8d 9f 3c 04 00 00 49 89 dc 49 c1 ec 03 43 0f b6 04 3c 84 c0 75 48 ff 0b <75> 1d 4c 8d b7 40 04 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 38 84
RSP: 0018:ffffc900001e0bc0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888028c521fc RCX: ffff888028c51dc0
RDX: 0000000000000100 RSI: ffffffff8adf1300 RDI: ffff888028c51dc0
RBP: 0000000000000001 R08: ffffffff8e1ff3ef R09: 1ffffffff1c3fe7d
R10: dffffc0000000000 R11: fffffbfff1c3fe7e R12: 1ffff1100518a43f
R13: 0000000000000001 R14: ffff8880548b7190 R15: dffffc0000000000
 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:2147
 __run_hrtimer kernel/time/hrtimer.c:1747 [inline]
 __hrtimer_run_queues+0x54a/0xd50 kernel/time/hrtimer.c:1811
 hrtimer_run_softirq+0x183/0x2a0 kernel/time/hrtimer.c:1828
 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:do_one_broadcast net/netlink/af_netlink.c:1429 [inline]
RIP: 0010:netlink_broadcast+0x1cb/0x10d0 net/netlink/af_netlink.c:1519
Code: 84 a7 0d 00 00 4d 89 f4 4c 8d ab 20 05 00 00 4c 89 e8 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 bf 0b 00 00 45 8b 75 00 44 89 f7 <89> ee e8 be 6f 19 f9 41 39 ee 75 0a e8 54 6e 19 f9 e9 21 01 00 00
RSP: 0018:ffffc9001c037920 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88801cef9000 RCX: ffff88801d7e9ce0
RDX: dffffc0000000000 RSI: ffffffff8a8c1120 RDI: 0000000000000f5c
RBP: 0000000000000000 R08: ffffffff90af9267 R09: 1ffffffff215f24c
R10: dffffc0000000000 R11: fffffbfff215f24d R12: ffff88805a1700d8
R13: ffff88801cef9520 R14: 0000000000000f5c R15: dffffc0000000000
 uevent_net_broadcast_tagged lib/kobject_uevent.c:372 [inline]
 kobject_uevent_net_broadcast+0x497/0x530 lib/kobject_uevent.c:412
 kobject_uevent_env+0x54c/0x8a0 lib/kobject_uevent.c:608
 device_add+0x91c/0xfb0 drivers/base/core.c:3678
 netdev_register_kobject+0x184/0x320 net/core/net-sysfs.c:2013
 register_netdevice+0x12dc/0x1b10 net/core/dev.c:10243
 ppp_unit_register drivers/net/ppp/ppp_generic.c:1229 [inline]
 ppp_dev_configure+0x874/0xad0 drivers/net/ppp/ppp_generic.c:1285
 ppp_create_interface drivers/net/ppp/ppp_generic.c:3362 [inline]
 ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1070 [inline]
 ppp_ioctl+0x699/0x1a50 drivers/net/ppp/ppp_generic.c:743
 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: 0033:0x7f937819cdd9
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:00007f937909d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9378415fa0 RCX: 00007f937819cdd9
RDX: 000000110e22fff6 RSI: 00000000c004743e RDI: 0000000000000006
RBP: 00007f9378232d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9378416038 R14: 00007f9378415fa0 R15: 00007ffc954a49e8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/01 22:47 linux-6.1.y 4931e0e1673d 753c55b9 .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.