syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=aa6/1/0x4000000000000002 softirq=59715/59716 fqs=5045 
	(t=10500 jiffies g=56037 q=108808)
NMI backtrace for cpu 1
CPU: 1 PID: 18057 Comm: syz-executor.3 Not tainted 5.6.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x183/0x1cf kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:475 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:549 [inline]
 rcu_pending kernel/rcu/tree.c:3030 [inline]
 rcu_sched_clock_irq.cold+0x51a/0xc37 kernel/rcu/tree.c:2276
 update_process_times+0x2d/0x70 kernel/time/timer.c:1726
 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:171
 tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1314
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline]
 smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1144
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:qlink_free mm/kasan/quarantine.c:151 [inline]
RIP: 0010:qlist_free_all+0x10c/0x150 mm/kasan/quarantine.c:167
Code: 50 08 48 8d 4a ff 83 e2 01 48 0f 45 c1 4c 8b 78 18 e9 37 ff ff ff e8 d3 ef c6 ff 48 83 3d 23 70 ff 07 00 74 39 48 89 df 57 9d <0f> 1f 44 00 00 4d 85 ed 75 96 49 c7 46 08 00 00 00 00 49 c7 06 00
RSP: 0018:ffffc900057e7d38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000007 RBX: 0000000000000282 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888043216b18 RDI: 0000000000000282
RBP: ffffc900057e7d68 R08: ffff888043216280 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff888097b4a000 R14: ffffc900057e7d78 R15: ffff88821bc50a80
 quarantine_reduce+0x15e/0x1a0 mm/kasan/quarantine.c:260
 __kasan_kmalloc.constprop.0+0xa3/0xe0 mm/kasan/common.c:496
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:523
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 __do_kmalloc mm/slab.c:3654 [inline]
 __kmalloc_track_caller+0x148/0x760 mm/slab.c:3671
 memdup_user+0x26/0xd0 mm/util.c:172
 strndup_user+0x77/0xd0 mm/util.c:231
 copy_mount_string fs/namespace.c:3009 [inline]
 __do_sys_mount fs/namespace.c:3301 [inline]
 __se_sys_mount fs/namespace.c:3293 [inline]
 __x64_sys_mount+0xe9/0x230 fs/namespace.c:3293
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45eeca
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 4d 8c fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 2a 8c fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f6586c77a68 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6586c786d4 RCX: 000000000045eeca
RDX: 00007f6586c77ae0 RSI: 0000000000000000 RDI: 00007f6586c77b00
RBP: 000000000076bf20 R08: 00007f6586c77b40 R09: 00007f6586c77ae0
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000ffffffff
R13: 0000000000000be8 R14: 00000000004cdcc6 R15: 000000000076bf2c