BUG: unable to handle kernel NULL pointer dereference in call_timer_fn

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 050272a0 Linux 4.14.177
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12728fcfe00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b24dc669afb42f8b
dashboard link: https://syzkaller.appspot.com/bug?extid=2d81b1c6aeaf80453a76
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2d81b1...@syzkaller.appspotmail.com

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: (null)
PGD a547e067 P4D a547e067 PUD a547f067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.177-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff87c76240 task.stack: ffffffff87c00000
RIP: 0010: (null)
RSP: 0018:ffff8880aea07d70 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff888000132a40 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffffffff87d842e0 RDI: 0000000000000000
RBP: 0000000000000101 R08: 0000000000004262 R09: ffffffff8a080b50
R10: ffffffff87c76ac8 R11: ffffffff87c76240 R12: ffff8880aea07db0
R13: 1ffff11015d40fb2 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000a547d000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
call_timer_fn+0x14a/0x650 kernel/time/timer.c:1279
expire_timers kernel/time/timer.c:1318 [inline]
__run_timers kernel/time/timer.c:1636 [inline]
__run_timers kernel/time/timer.c:1604 [inline]
run_timer_softirq+0x52a/0x1390 kernel/time/timer.c:1649
__do_softirq+0x254/0x9bf kernel/softirq.c:288
invoke_softirq kernel/softirq.c:368 [inline]
irq_exit+0x15b/0x1a0 kernel/softirq.c:409
exiting_irq arch/x86/include/asm/apic.h:648 [inline]
smp_apic_timer_interrupt+0x141/0x5e0 arch/x86/kernel/apic/apic.c:1102
apic_timer_interrupt+0x8f/0xa0 arch/x86/entry/entry_64.S:792
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
RSP: 0018:ffffffff87c07e78 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff0fa2cd4 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffffffff87c76ac4
RBP: ffffffff87d16690 R08: 1ffffffff1124101 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff0f8ec48
R13: ffffffff87c76240 R14: 0000000000000000 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
default_idle+0x47/0x370 arch/x86/kernel/process.c:566
cpuidle_idle_call kernel/sched/idle.c:156 [inline]
do_idle+0x250/0x3c0 kernel/sched/idle.c:246
cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:351
start_kernel+0x659/0x676 init/main.c:708
secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240
Code: Bad RIP value.
RIP: (null) RSP: ffff8880aea07d70
CR2: 0000000000000000
---[ end trace 25829c98cad975a8 ]---


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.