------------[ cut here ]------------
WARNING: CPU: 0 PID: 20468 at kernel/rcu/tree_stall.h:1001 rcu_check_gp_start_stall+0x2dc/0x460 kernel/rcu/tree_stall.h:993
Modules linked in:
CPU: 0 PID: 20468 Comm: syz.6.4252 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:rcu_check_gp_start_stall+0x2dc/0x460 kernel/rcu/tree_stall.h:1001
Code: ff ff ff 48 c7 c7 a0 94 33 97 be 04 00 00 00 e8 8a 4c 6e 00 48 89 df b8 01 00 00 00 87 05 dc a6 c1 15 85 c0 0f 85 19 ff ff ff <0f> 0b 48 81 ff 40 73 13 8d 74 47 48 c7 c0 2c 97 8c 8e 48 c1 e8 03
RSP: 0018:ffffc90000007bb8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffffffff8d137340 RCX: ffffffff8171edb6
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff8d137340
RBP: ffffc90000007e30 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff2e67294 R12: 0000000000002904
R13: 1ffff92000000f94 R14: 0000000000000a02 R15: dffffc0000000000
FS:  000055557ff4a500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0c4dbeb880 CR3: 0000000073c34000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 rcu_core+0x5ec/0x17f0 kernel/rcu/tree.c:2462
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5794
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc9000bf9fa60 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 3e775cad4d2c8900
RDX: 0000000000000000 RSI: ffffffff8acade60 RDI: ffffffff8b1d4020
RBP: ffffc9000bf9fb68 R08: dffffc0000000000 R09: 1ffffffff223e0a6
R10: dffffc0000000000 R11: fffffbfff223e0a7 R12: 1ffff920017f3f58
R13: ffff88807c9cea20 R14: 0000000000000246 R15: dffffc0000000000
 __might_fault+0xc6/0x120 mm/memory.c:5968
 _copy_to_user+0x2a/0xa0 lib/usercopy.c:36
 copy_to_user include/linux/uaccess.h:191 [inline]
 copy_siginfo_to_user+0x24/0xa0 kernel/signal.c:3385
 x64_setup_rt_frame+0x749/0xc30 arch/x86/kernel/signal_64.c:194
 setup_rt_frame arch/x86/kernel/signal.c:223 [inline]
 handle_signal arch/x86/kernel/signal.c:267 [inline]
 arch_do_signal_or_restart+0x411/0x7b0 arch/x86/kernel/signal.c:312
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:294 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:305
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0c4da517c3
Code: 00 00 00 0f 1f 40 00 41 89 fb 44 8d 56 04 4c 8d 0d 52 08 3c 00 89 f0 4c 8d 05 49 e8 3b 00 89 c2 81 e2 ff 1f 00 00 49 8b 0c d1 <48> 39 f1 74 28 48 85 c9 74 29 45 38 1c 10 75 23 83 c0 01 44 39 d0
RSP: 002b:00007ffff4ace658 EFLAGS: 00000206
RAX: 0000000084348f14 RBX: ffffffff84348f14 RCX: ffffffff81792f14
RDX: 0000000000000f14 RSI: ffffffff84348f14 RDI: 000000000000000a
RBP: 0000000000000000 R08: 00007f0c4de10000 R09: 00007f0c4de12000
R10: 0000000084348f18 R11: 000000000000000a R12: 00007f0c4de26038
R13: 000000000001a750 R14: ffffffff84348aa9 R15: 00007f0c4e955720
 </TASK>
----------------
Code disassembly (best guess):
   0:	f7 84 24 80 00 00 00 	testl  $0x200,0x80(%rsp)
   7:	00 02 00 00
   b:	43 c6 44 3c 04 f8    	movb   $0xf8,0x4(%r12,%r15,1)
  11:	0f 85 f0 00 00 00    	jne    0x107
  17:	41 f7 c6 00 02 00 00 	test   $0x200,%r14d
  1e:	74 01                	je     0x21
  20:	fb                   	sti
  21:	48 c7 44 24 60 0e 36 	movq   $0x45e0360e,0x60(%rsp)
  28:	e0 45
* 2a:	4b c7 04 3c 00 00 00 	movq   $0x0,(%r12,%r15,1) <-- trapping instruction
  31:	00
  32:	43 c7 44 3c 08 00 00 	movl   $0x0,0x8(%r12,%r15,1)
  39:	00 00
  3b:	65                   	gs
  3c:	48                   	rex.W
  3d:	8b                   	.byte 0x8b
  3e:	04 25                	add    $0x25,%al