syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=9049, q=84 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294956419-4294945916), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g9049 f0x2 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:27088 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </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 PID: 5819 Comm: syz-executor233 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:hlock_class kernel/locking/lockdep.c:223 [inline]
RIP: 0010:mark_lock+0x56/0x320 kernel/locking/lockdep.c:4656
Code: 03 42 0f b6 04 28 84 c0 0f 85 74 02 00 00 41 0f b6 47 02 24 03 3c 01 bd 09 00 00 00 83 dd 00 41 bc 01 00 00 00 89 e9 41 d3 e4 <4d> 8d 7e 20 4c 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 22 02
RSP: 0018:ffffc9000471f8c0 EFLAGS: 00000002
RAX: 00000000000501a7 RBX: ffff88802b945a00 RCX: 0000000000000003
RDX: 0000000000000003 RSI: ffff88802b9464e0 RDI: ffff88802b945a00
RBP: 0000000000000003 R08: dffffc0000000000 R09: 1ffffffff21b4ea6
R10: dffffc0000000000 R11: fffffbfff21b4ea7 R12: 0000000000000008
R13: dffffc0000000000 R14: ffff88802b9464e0 R15: ffff88802b946500
FS:  0000555568a22480(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 000000007a429000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 mark_usage kernel/locking/lockdep.c:4579 [inline]
 __lock_acquire+0x110b/0x7c80 kernel/locking/lockdep.c:5091
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __might_fault+0xc6/0x120 mm/memory.c:5946
 _copy_from_user+0x2a/0xe0 lib/usercopy.c:14
 copy_from_user include/linux/uaccess.h:183 [inline]
 restore_sigcontext arch/x86/kernel/signal_64.c:59 [inline]
 __ia32_sys_rt_sigreturn+0x27a/0x7b0 arch/x86/kernel/signal_64.c:266
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f187ceb2d29
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007ffc421e7b00 EFLAGS: 00000206 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f187ceb2d29
RDX: 00007ffc421e7b00 RSI: 00007ffc421e7c30 RDI: 0000000000000021
RBP: 0000000000000000 R08: 00007f187cf6c488 R09: 00007f187cf6c488
R10: 0000000000000000 R11: 0000000000000206 R12: 00007f187cf6c488
R13: 00007ffc421e80dc R14: 0000000000000000 R15: 431bde82d7b634db
 </TASK>