syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=35749, q=4 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294988743-4294978240), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g35749 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:27000 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6561
 schedule+0xbf/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8025 Comm: syz.3.1102 Not tainted 6.1.134-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:lock_acquire+0x2e/0x5a0 kernel/locking/lockdep.c:5630
Code: 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48 81 ec 20 01 00 00 4c 89 4c 24 28 4c 89 44 24 38 48 89 4c 24 30 89 54 24 1c 41 89 f6 <48> 89 7c 24 20 65 48 8b 04 25 28 00 00 00 48 89 84 24 00 01 00 00
RSP: 0018:ffffc9000472f920 EFLAGS: 00000282
RAX: ffffffff81cd5593 RBX: ffff888074ea40a8 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880202e1f58
RBP: ffffc9000472fa78 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff1100e9d4815
FS:  00007fa0ae8a16c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2f5e6b CR3: 0000000030ecb000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __might_fault+0xbd/0x110 mm/memory.c:5852
 __copy_to_user include/linux/uaccess.h:111 [inline]
 save_xstate_epilog arch/x86/kernel/fpu/signal.c:127 [inline]
 copy_fpstate_to_sigframe+0xb16/0xda0 arch/x86/kernel/fpu/signal.c:245
 get_sigframe arch/x86/kernel/signal.c:297 [inline]
 __setup_rt_frame arch/x86/kernel/signal.c:472 [inline]
 setup_rt_frame arch/x86/kernel/signal.c:784 [inline]
 handle_signal arch/x86/kernel/signal.c:828 [inline]
 arch_do_signal_or_restart+0x6eb/0x12a0 arch/x86/kernel/signal.c:873
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
 do_syscall_64+0x47/0x80 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa0ad98e169
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:00007fa0ae8a10e8 EFLAGS: 00000246
RAX: fffffffffffffffc RBX: 00007fa0adbb5fa8 RCX: 00007fa0ad98e169
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fa0adbb5fa8
RBP: 00007fa0adbb5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa0adbb5fac
R13: 0000000000000000 R14: 00007ffc72cc66f0 R15: 00007ffc72cc67d8
 </TASK>