kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 5197 Comm: syz-executor7 Not tainted 4.13.0-next-20170908+ #18
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff8800552d0600 task.stack: ffff880055e40000
RIP: 0010:__hlist_del include/linux/list.h:650 [inline]
RIP: 0010:detach_timer kernel/time/timer.c:791 [inline]
RIP: 0010:expire_timers kernel/time/timer.c:1309 [inline]
RIP: 0010:__run_timers+0x619/0xb90 kernel/time/timer.c:1620
RSP: 0000:ffff88006df07968 EFLAGS: 00010806
RAX: 1bd5a00000000041 RBX: ffff88005805b7c0 RCX: 1ffff1000dbe0f76
RDX: ffff88006df07bb0 RSI: ffffffff85b380e0 RDI: dead000000000208
RBP: ffff88006df07c58 R08: ffff88006df072b8 R09: ffff88006df072b0
R10: ffff88006df07228 R11: 1ffff1000aa5a353 R12: ffff88005805b7c8
R13: dffffc0000000000 R14: dead000000000200 R15: ffff88006df07c30
FS:  00000000020aa940(0000) GS:ffff88006df00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001ddbc2a000 CR3: 000000005624d000 CR4: 00000000000026e0
Call Trace:
 <IRQ>
 run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1646
 __do_softirq+0x2bb/0xbd0 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x1d3/0x210 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:638 [inline]
 smp_apic_timer_interrupt+0x177/0x710 arch/x86/kernel/apic/apic.c:1048
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:577
 </IRQ>
RIP: 0010:block_page_mkwrite+0xa5/0x3a0 fs/buffer.c:2519
RSP: 0000:ffff880055e477d0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000000 RBX: ffffea00016759c0 RCX: 0000000000000000
RDX: 1ffff1000d5e7e56 RSI: ffff880055e47be8 RDI: ffff88006af3f2b0
RBP: ffff880055e47870 R08: ffff880055e47150 R09: ffff880055e47148
R10: ffff880055e470c0 R11: 1ffff1000aa5a353 R12: 1ffff1000abc8efd
R13: ffff88006af3f210 R14: ffff880055e47848 R15: dffffc0000000000
 ext4_page_mkwrite+0xd60/0x1240 fs/ext4/inode.c:6029
 do_page_mkwrite+0x141/0x490 mm/memory.c:2353
 do_shared_fault mm/memory.c:3645 [inline]
 do_fault mm/memory.c:3684 [inline]
 handle_pte_fault mm/memory.c:3910 [inline]
 __handle_mm_fault+0x1aab/0x39c0 mm/memory.c:4034
 handle_mm_fault+0x334/0x8d0 mm/memory.c:4071
 __do_page_fault+0x4f6/0xb60 arch/x86/mm/fault.c:1445
 do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1520
 do_async_page_fault+0x72/0xc0 arch/x86/kernel/kvm.c:266
 async_page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1069
RIP: 0033:0x4021a2
RSP: 002b:0000000000a5f890 EFLAGS: 00010287
RAX: 0000001ddbc2a000 RBX: 0000000000708000 RCX: 000000000000012d
RDX: 0000001ddcc20000 RSI: 00000000a12b012e RDI: 00000000a12b012a
RBP: 0000000000000284 R08: 000000000000012a R09: 000001160000001d
R10: 0000000000a5f960 R11: 0000000000000206 R12: 0000000000001e9c
R13: 00000000000023b9 R14: 0000000000000000 R15: 000000003cb3c37f
Code: 4d 85 f6 4c 89 32 48 89 95 58 fd ff ff 42 c6 04 28 f8 74 26 e8 49 33 10 00 49 8d 7e 08 48 8b 95 58 fd ff ff 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 0f 85 b5 04 00 00 49 89 56 08 e8 23 33 10 00 4c 
RIP: __hlist_del include/linux/list.h:650 [inline] RSP: ffff88006df07968
RIP: detach_timer kernel/time/timer.c:791 [inline] RSP: ffff88006df07968
RIP: expire_timers kernel/time/timer.c:1309 [inline] RSP: ffff88006df07968
RIP: __run_timers+0x619/0xb90 kernel/time/timer.c:1620 RSP: ffff88006df07968
---[ end trace c6c16a976489f3c5 ]---