Message-ID: <6941a5f6.a70a0220.25eec0.0005.GAE@google.com>
Date: Tue, 16 Dec 2025 10:33:26 -0800
From: syzbot <syzbot+a60fc566f2bff263d4c4@...kaller.appspotmail.com>
To: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com, 
	john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org, 
	linux-kernel@...r.kernel.org, martin.lau@...ux.dev, netdev@...r.kernel.org, 
	sdf@...ichev.me, song@...nel.org, syzkaller-bugs@...glegroups.com, 
	yonghong.song@...ux.dev
Subject: [syzbot] [bpf?] INFO: rcu detected stall in unwind_get_return_address (2)

Hello,

syzbot found the following issue on:

HEAD commit:    8f7aa3d3c732 Merge tag 'net-next-6.19' of git://git.kernel..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=143dd592580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9e5198eaf003f1d1
dashboard link: https://syzkaller.appspot.com/bug?extid=a60fc566f2bff263d4c4
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=123dd592580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5fe312c4cf90/disk-8f7aa3d3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c7a1f54ef730/vmlinux-8f7aa3d3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/64a3779458bb/bzImage-8f7aa3d3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a60fc566f2bff263d4c4@...kaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6092/1:b..l
rcu: 	(detected by 0, t=10504 jiffies, g=14093, q=390 ncpus=2)
task:syz.0.24        state:R  running task     stack:25784 pid:6092  tgid:6092  ppid:5948   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6863
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7190
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__rcu_read_lock+0x39/0x60 kernel/rcu/tree_plugin.h:420
Code: 81 c3 84 04 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 18 ff 03 8b 03 3d 00 00 00 40 7d 07 <5b> e9 41 2b a4 09 cc 90 0f 0b 90 eb f3 89 d9 80 e1 07 80 c1 03 38
RSP: 0018:ffffc90002ea7920 EFLAGS: 00000283
RAX: 0000000000000001 RBX: ffff88802e7d6004 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffffff8d952009 RDI: 00007f070e78f749
RBP: 0000000000000001 R08: ffffffff81abc2cd R09: ffffffff8df41cc0
R10: ffffc90002ea7a18 R11: ffffffff81ad4ad0 R12: ffff88802e7d5b80
R13: 0000000000000000 R14: 00007f070e78f749 R15: 1ffff920005d4f42
 rcu_read_lock include/linux/rcupdate.h:865 [inline]
 is_bpf_text_address+0x1f/0x2b0 kernel/bpf/core.c:744
 kernel_text_address+0xa5/0xe0 kernel/extable.c:125
 __kernel_text_address+0xd/0x40 kernel/extable.c:79
 unwind_get_return_address+0x4d/0x90 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0xfc/0x150 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:56
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:559
 slab_free_hook mm/slub.c:2501 [inline]
 slab_free mm/slub.c:6663 [inline]
 kmem_cache_free+0x475/0x620 mm/slub.c:6774
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0xff/0x4f0 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2e3/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f070e78f749
RSP: 002b:00007ffdac4cad28 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f070e9e7da0 RCX: 00007f070e78f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f070e9e7da0 R08: 0000000000000000 R09: 00000007ac4cb01f
R10: 000000000003fd8c R11: 0000000000000246 R12: 000000000001c975
R13: 00007f070e9e5fa0 R14: ffffffffffffffff R15: 0000000000000003
 </TASK>
rcu: rcu_preempt kthread starved for 8379 jiffies! g14093 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27520 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 935 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: wg-crypt-wg1 wg_packet_decrypt_worker
RIP: 0010:check_kcov_mode kernel/kcov.c:185 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:246 [inline]
RIP: 0010:__sanitizer_cov_trace_switch+0xb3/0x130 kernel/kcov.c:351
Code: 77 4e 8b 54 ce 10 65 44 8b 1d b9 9f b5 10 41 81 e3 00 01 ff 00 74 13 41 81 fb 00 01 00 00 75 d9 41 83 b8 6c 16 00 00 00 74 cf <45> 8b 98 48 16 00 00 41 83 fb 03 75 c2 4d 8b 98 50 16 00 00 45 8b
RSP: 0018:ffffc90003c667a0 EFLAGS: 00000046
RAX: 0000000000000020 RBX: 0000000000000004 RCX: 0000000000000005
RDX: ffffffff81c32a05 RSI: ffffffff8df99b60 RDI: 0000000000000004
RBP: 0000003403a09659 R08: ffff888024e28000 R09: 0000000000000011
R10: 0000000000000011 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff88801d2b2010 R14: ffff88801d2b2894 R15: 00000000000b4004
FS:  0000000000000000(0000) GS:ffff8881261b1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30663fff CR3: 0000000030904000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rb_event_length+0x45/0x400 kernel/trace/ring_buffer.c:222
 rb_read_data_buffer+0x438/0x580 kernel/trace/ring_buffer.c:1823
 check_buffer+0x28a/0x750 kernel/trace/ring_buffer.c:4394
 __rb_reserve_next+0x592/0xdb0 kernel/trace/ring_buffer.c:4493
 rb_reserve_next_event kernel/trace/ring_buffer.c:4630 [inline]
 ring_buffer_lock_reserve+0xbb5/0x1010 kernel/trace/ring_buffer.c:4689
 __trace_buffer_lock_reserve kernel/trace/trace.c:1081 [inline]
 trace_event_buffer_lock_reserve+0x1d0/0x6f0 kernel/trace/trace.c:2799
 trace_event_buffer_reserve+0x248/0x340 kernel/trace/trace_events.c:672
 do_trace_event_raw_event_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_event_raw_event_bpf_trace_printk+0x100/0x260 kernel/trace/bpf_trace.h:11
 __do_trace_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_bpf_trace_printk+0x153/0x1b0 kernel/trace/bpf_trace.h:11
 ____bpf_trace_printk kernel/trace/bpf_trace.c:379 [inline]
 bpf_trace_printk+0x11e/0x190 kernel/trace/bpf_trace.c:362
 bpf_prog_b1367f0be6c54012+0x39/0x3f
 bpf_dispatcher_nop_func include/linux/bpf.h:1376 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run1+0x27f/0x4c0 kernel/trace/bpf_trace.c:2115
 __bpf_trace_rcu_utilization+0xa1/0xf0 include/trace/events/rcu.h:27
 __traceiter_rcu_utilization+0x7a/0xb0 include/trace/events/rcu.h:27
 __do_trace_rcu_utilization include/trace/events/rcu.h:27 [inline]
 trace_rcu_utilization+0x191/0x1c0 include/trace/events/rcu.h:27
 rcu_note_context_switch+0xc9/0x1120 kernel/rcu/tree_plugin.h:330
 __schedule+0x346/0x5000 kernel/sched/core.c:6748
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7047
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:7071
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __local_bh_enable_ip+0x13e/0x1c0 kernel/softirq.c:457
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 ptr_ring_consume_bh include/linux/ptr_ring.h:377 [inline]
 wg_packet_decrypt_worker+0xca4/0xd40 drivers/net/wireguard/receive.c:499
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>


---
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