[syzbot] [bpf?] INFO: rcu detected stall in task_work_add

[syzbot <syzbot+f2cf09711ff194bc2c22@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3b5ca25ecfa8 Merge branch 'net-don-t-use-pk-through-printk..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=104365a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2ae1da3a7f4a6ba4
dashboard link: https://syzkaller.appspot.com/bug?extid=f2cf09711ff194bc2c22
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=140b0da2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3a41dee6422d/disk-3b5ca25e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/37991dc02c89/vmlinux-3b5ca25e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/48eac1c2fff5/bzImage-3b5ca25e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2cf09711ff194bc2c22@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6488/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=19581, q=865 ncpus=2)
task:syz.6.33        state:R  running task     stack:25096 pid:6488  tgid:6488  ppid:6264   task_flags:0x400040 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7288
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:197
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_acquire+0x175/0x360 kernel/locking/lockdep.c:5872
Code: 00 00 00 00 9c 8f 44 24 30 f7 44 24 30 00 02 00 00 0f 85 cd 00 00 00 f7 44 24 08 00 02 00 00 74 01 fb 65 48 8b 05 eb 93 02 11 <48> 3b 44 24 58 0f 85 f2 00 00 00 48 83 c4 60 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc900047776f0 EFLAGS: 00000206
RAX: c2093f235efbe900 RBX: 0000000000000000 RCX: c2093f235efbe900
RDX: 0000000000000001 RSI: ffffffff8dba39e3 RDI: ffffffff8be32680
RBP: ffffffff81cea1f6 R08: 0000000000000000 R09: ffffffff81cea1f6
R10: ffffc90004777878 R11: ffffffff81ac3890 R12: 0000000000000002
R13: ffffffff8e139ee0 R14: 0000000000000000 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:841 [inline]
 is_bpf_text_address+0x47/0x2b0 kernel/bpf/core.c:776
 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:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 task_work_add+0xb1/0x420 kernel/task_work.c:65
 __fput_deferred+0x154/0x390 fs/file_table.c:529
 fput_close+0x119/0x200 fs/file_table.c:585
 filp_close+0x27/0x40 fs/open.c:1561
 __range_close fs/file.c:767 [inline]
 __do_sys_close_range fs/file.c:826 [inline]
 __se_sys_close_range+0x359/0x650 fs/file.c:790
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fed93f8ebe9
RSP: 002b:00007ffcb5611318 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: ffffffffffffffda RBX: 00007fed941b7da0 RCX: 00007fed93f8ebe9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fed941b7da0 R08: 0000000000000000 R09: 00000006b561160f
R10: 00007fed941b7cb0 R11: 0000000000000246 R12: 0000000000057219
R13: 00007fed941b6090 R14: ffffffffffffffff R15: 0000000000000003
 </TASK>
rcu: rcu_preempt kthread starved for 1596 jiffies! g19581 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:27160 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 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+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 6401 Comm: napi/wg0-0 Not tainted 6.16.0-syzkaller-12122-g3b5ca25ecfa8 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:finish_task_switch+0x26b/0x950 kernel/sched/core.c:5225
Code: 0f 84 3c 01 00 00 48 85 db 0f 85 63 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 cf 37 ea 09 e8 5a 3f 36 00 fb 4c 8b 65 c0 <49> 8d bc 24 18 16 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc9000458fa78 EFLAGS: 00000286
RAX: e330458c080e4500 RBX: 0000000000000000 RCX: e330458c080e4500
RDX: 0000000000000000 RSI: ffffffff8d9b49fa RDI: ffffffff8be32680
RBP: ffffc9000458fad0 R08: ffffffff8fa34737 R09: 1ffffffff1f468e6
R10: dffffc0000000000 R11: fffffbfff1f468e7 R12: ffff8880252d0000
R13: dffffc0000000000 R14: ffff8880256a3c00 R15: ffff8880b873ab58
FS:  0000000000000000(0000) GS:ffff888125d21000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055ea52750000 CR3: 0000000077f62000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5360 [inline]
 __schedule+0x17a0/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 napi_thread_wait net/core/dev.c:7583 [inline]
 napi_threaded_poll+0xfa/0x2b0 net/core/dev.c:7634
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
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