[v6.1] INFO: rcu detected stall in ppp_ioctl (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4931e0e1673d Linux 6.1.170
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1170f506580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=319e3b2e98552460a879
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cd62baf6f839/disk-4931e0e1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/28b9d34fdc6c/vmlinux-4931e0e1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5056ec0ca104/bzImage-4931e0e1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+319e3b...@syzkaller.appspotmail.com

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>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup