syzbot


INFO: rcu detected stall in ppp_ioctl

Status: upstream: reported on 2025/12/23 20:21
Reported-by: syzbot+641cec3c777db56565d3@syzkaller.appspotmail.com
First crash: 19d, last: 19d
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in ppp_ioctl 1 1 467d 467d 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 425d 440d 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 87d 87d 0/3 upstream: reported on 2025/10/16 16:32
android-5-15 BUG: soft lockup in ppp_ioctl 1 5 505d 632d 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: 	0-....: (1 ticks this GP) idle=295/1/0x4000000000000002 softirq=21415/21415 fqs=2100 
	(detected by 1, t=10503 jiffies, g=30421, q=2370)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8915 Comm: syz.5.1110 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:asm_sysvec_irq_work+0x0/0x20 arch/x86/include/asm/idtentry.h:707
Code: e9 a5 03 00 00 90 90 90 90 90 0f 01 ca fc 6a ff e8 a5 02 00 00 48 89 c4 48 89 e7 e8 fa ba e1 ff e9 85 03 00 00 90 90 90 90 90 <0f> 01 ca fc 6a ff e8 85 02 00 00 48 89 c4 48 89 e7 e8 ca bf e1 ff
RSP: 0018:ffffc90000007ab8 EFLAGS: 00000006
RAX: 80be8ae255154e00 RBX: 1ffff92000000f60 RCX: 80be8ae255154e00
RDX: dffffc0000000000 RSI: ffffffff8a0b1be0 RDI: ffffffff8a59e800
RBP: ffffc90000007bb8 R08: dffffc0000000000 R09: fffffbfff1ff541f
R10: fffffbfff1ff541f R11: 1ffffffff1ff541e R12: ffffffff8c120c00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
FS:  00007fa8639546c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110e22fff6 CR3: 000000002298f000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
RIP: 0010:rcu_read_unlock_special+0x84/0x480 kernel/rcu/tree_plugin.h:674
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 ed 11 9e 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc90000007ae0 EFLAGS: 00000206
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x53d/0xc40 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 handle_softirqs+0x328/0x820 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x12f/0x220 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:unwind_next_frame+0x3ce/0x1d90 arch/x86/kernel/unwind_orc.c:461
Code: b6 04 28 84 c0 0f 85 87 14 00 00 41 c6 06 01 48 c7 c2 80 86 08 8a 4c 8d 72 04 4c 8d 7a 05 4d 89 f4 49 c1 ec 03 43 0f b6 04 2c <84> c0 48 89 14 24 0f 85 af 13 00 00 4c 89 f8 48 c1 e8 03 42 0f b6
RSP: 0018:ffffc900014df2c8 EFLAGS: 00000a07
RAX: 0000000000000000 RBX: ffffc900014df388 RCX: ffffffff8d7ee484
RDX: ffffffff8dedecb2 RSI: ffffffff8dedecb2 RDI: ffffffff8134794c
RBP: ffffffff81c28110 R08: 0000000000000001 R09: 0000000000000000
R10: fffff5200029be7d R11: 1ffff9200029be7b R12: 1ffffffff1bdbd96
R13: dffffc0000000000 R14: ffffffff8dedecb6 R15: ffffffff8dedecb7
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 save_stack+0xf3/0x1e0 mm/page_owner.c:119
 __set_page_owner+0x41/0x2d0 mm/page_owner.c:181
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 __pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
 pte_alloc_one+0x80/0x2f0 arch/x86/mm/pgtable.c:33
 do_fault_around mm/memory.c:4237 [inline]
 do_read_fault mm/memory.c:4258 [inline]
 do_fault mm/memory.c:4392 [inline]
 handle_pte_fault mm/memory.c:4650 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x2515/0x43b0 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0010:__get_user_4+0x1c/0x30 arch/x86/lib/getuser.S:85
Code: 01 ca c3 90 90 90 90 90 90 90 90 90 90 90 48 ba fd ef ff ff ff 7f 00 00 48 39 d0 0f 83 90 00 00 00 48 19 d2 48 21 d0 0f 01 cb <8b> 10 31 c0 0f 01 ca c3 90 90 90 90 90 90 90 90 90 90 90 90 48 ba
RSP: 0018:ffffc900014dfd98 EFLAGS: 00050206
RAX: 000000110e22fff6 RBX: ffff88807e42cf80 RCX: 80be8ae255154e00
RDX: ffffffffffffffff RSI: ffffffff8a0b2e80 RDI: ffffffff8a59e800
RBP: ffffc900014dfed8 R08: dffffc0000000000 R09: fffffbfff1ad26b6
R10: fffffbfff1ad26b6 R11: 1ffffffff1ad26b5 R12: 00000000c004743e
R13: ffff888025abd830 R14: ffff888025abd680 R15: 1ffff11004b57b06
 ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1067 [inline]
 ppp_ioctl+0x377/0x1960 drivers/net/ppp/ppp_generic.c:742
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa8656ed749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa863954038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa865943fa0 RCX: 00007fa8656ed749
RDX: 000000110e22fff6 RSI: 00000000c004743e RDI: 0000000000000006
RBP: 00007fa865771f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa865944038 R14: 00007fa865943fa0 R15: 00007ffc3eb7c438
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/23 20:21 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in ppp_ioctl
* Struck through repros no longer work on HEAD.