Date:   Sun, 06 Sep 2020 11:40:17 -0700
From:   syzbot <syzbot+cb3b69ae80afd6535b0e@...kaller.appspotmail.com>
To:     bp@...en8.de, fweisbec@...il.com, hpa@...or.com,
        jpoimboe@...hat.com, linux-kernel@...r.kernel.org, mbenes@...e.cz,
        mingo@...nel.org, mingo@...hat.com, paulmck@...nel.org,
        peterz@...radead.org, shile.zhang@...ux.alibaba.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de, x86@...nel.org
Subject: Re: INFO: rcu detected stall in smp_call_function

syzbot has found a reproducer for the following issue on:

HEAD commit:    dd9fb9bb Merge tags 'auxdisplay-for-linus-v5.9-rc4', 'clan..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=124893e1900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bd46548257448703
dashboard link: https://syzkaller.appspot.com/bug?extid=cb3b69ae80afd6535b0e
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13727231900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132c9fc9900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cb3b69ae80afd6535b0e@...kaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=932/1/0x4000000000000002 softirq=9344/9345 fqs=5247 
	(detected by 1, t=10502 jiffies, g=10529, q=124891)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8110 Comm: syz-executor267 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:91 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:108 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:134 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:165 [inline]
RIP: 0010:check_memory_region_inline mm/kasan/generic.c:183 [inline]
RIP: 0010:check_memory_region+0xdb/0x180 mm/kasan/generic.c:192
Code: 80 38 00 74 f2 48 89 c2 b8 01 00 00 00 48 85 d2 75 56 5b 5d 41 5c c3 48 85 d2 74 5e 48 01 ea eb 09 48 83 c0 01 48 39 d0 74 50 <80> 38 00 74 f2 eb d4 41 bc 08 00 00 00 48 89 ea 45 29 dc 4d 8d 1c
RSP: 0018:ffffc90000007090 EFLAGS: 00000086
RAX: fffff52000000e30 RBX: fffff52000000e3c RCX: ffffffff81339c7a
RDX: fffff52000000e3c RSI: 0000000000000060 RDI: ffffc90000007180
RBP: fffff52000000e30 R08: 0000000000000001 R09: ffffc900000071df
R10: fffff52000000e3b R11: 0000000000000001 R12: 0000000000000060
R13: 0000000000000000 R14: 000000000000007f R15: ffffc90000007180
FS:  0000000000cf9880(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000008319c CR3: 000000009f579000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 memset+0x20/0x40 mm/kasan/common.c:84
 memset include/linux/string.h:391 [inline]
 __unwind_start+0x2a/0x800 arch/x86/kernel/unwind_orc.c:630
 unwind_start arch/x86/include/asm/unwind.h:60 [inline]
 perf_callchain_kernel+0x2f0/0x6a0 arch/x86/events/core.c:2447
 get_perf_callchain+0x16e/0x620 kernel/events/callchain.c:200
 perf_callchain+0x165/0x1c0 kernel/events/core.c:6985
 perf_prepare_sample+0x8fd/0x1d40 kernel/events/core.c:7012
 __perf_event_output kernel/events/core.c:7170 [inline]
 perf_event_output_forward+0xf3/0x270 kernel/events/core.c:7190
 __perf_event_overflow+0x13c/0x370 kernel/events/core.c:8845
 perf_swevent_overflow kernel/events/core.c:8921 [inline]
 perf_swevent_event+0x347/0x550 kernel/events/core.c:8949
 perf_tp_event+0x2e4/0xb50 kernel/events/core.c:9377
 perf_trace_run_bpf_submit+0x11c/0x200 kernel/events/core.c:9351
 perf_trace_preemptirq_template+0x289/0x440 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle include/trace/events/preemptirq.h:40 [inline]
 trace_irq_enable_rcuidle include/trace/events/preemptirq.h:40 [inline]
 trace_hardirqs_on+0x18a/0x220 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x12/0x20 arch/x86/include/asm/idtentry.h:611
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
RIP: 0010:rcu_read_unlock_special kernel/rcu/tree_plugin.h:630 [inline]
RIP: 0010:__rcu_read_unlock+0x26e/0x530 kernel/rcu/tree_plugin.h:395
Code: ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 a3 02 00 00 48 83 3d d5 9c 54 08 00 0f 84 18 02 00 00 4c 89 e7 57 9d <0f> 1f 44 00 00 e9 07 fe ff ff 0f 0b e9 41 fe ff ff e8 5c b1 52 00
RSP: 0018:ffffc90000007b40 EFLAGS: 00000282
RAX: 1ffffffff136c789 RBX: ffffffff89bd9a80 RCX: 0000000000000002
RDX: dffffc0000000000 RSI: 0000000000000101 RDI: 0000000000000282
RBP: 0000000000000001 R08: 0000000000000001 R09: ffffffff8c5f4a97
R10: fffffbfff18be952 R11: 0000000000000001 R12: 0000000000000282
R13: 0000000000000200 R14: ffff8880ae636c00 R15: 0000000000000000
 rcu_read_unlock include/linux/rcupdate.h:687 [inline]
 mld_sendpack+0x742/0xdb0 net/ipv6/mcast.c:1690
 mld_send_initial_cr.part.0+0x106/0x150 net/ipv6/mcast.c:2096
 mld_send_initial_cr net/ipv6/mcast.c:1191 [inline]
 mld_dad_timer_expire+0x1c7/0x6a0 net/ipv6/mcast.c:2115
 call_timer_fn+0x1ac/0x760 kernel/time/timer.c:1413
 expire_timers kernel/time/timer.c:1458 [inline]
 __run_timers.part.0+0x67c/0xaa0 kernel/time/timer.c:1755
 __run_timers kernel/time/timer.c:1736 [inline]
 run_timer_softirq+0xae/0x1a0 kernel/time/timer.c:1768
 __do_softirq+0x1f7/0xa91 kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x9d/0xd0 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu kernel/softirq.c:423 [inline]
 irq_exit_rcu+0x235/0x280 kernel/softirq.c:435
 sysvec_apic_timer_interrupt+0x51/0xf0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
RIP: 0010:generic_exec_single+0x2b6/0x430 kernel/smp.c:172
Code: 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 2d 01 00 00 48 83 3d 82 fd 4c 08 00 0f 84 f3 00 00 00 e8 2f 0c 0b 00 48 89 df 57 9d <0f> 1f 44 00 00 45 31 e4 e9 34 fe ff ff e8 18 0c 0b 00 0f 0b e9 95
RSP: 0018:ffffc90009cbfb08 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000293 RCX: 0000000000000006
RDX: ffff88809054a380 RSI: ffffffff81693ed1 RDI: 0000000000000293
RBP: 0000000000000200 R08: 0000000000000001 R09: ffffffff8c5f4ab7
R10: fffffbfff18be956 R11: 0000000000000001 R12: ffffc90009cbfb80
R13: ffffffff818dc1d0 R14: ffffc90009cbfc48 R15: 1ffff92001397f9e
 smp_call_function_single+0x186/0x4f0 kernel/smp.c:379
 task_function_call+0xd7/0x160 kernel/events/core.c:116
 perf_install_in_context+0x2cb/0x550 kernel/events/core.c:2895
 __do_sys_perf_event_open+0x1c31/0x2cb0 kernel/events/core.c:11992
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x443f79
Code: e8 2c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 0b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffe1fb0778 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000443f79
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000100
RBP: 000000000008319c R08: 0000000000000000 R09: 0000000100000009
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000404da0 R14: 0000000000000000 R15: 0000000000000000
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 0.000 msecs

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