Date:   Mon, 12 Feb 2018 07:54:48 -0800
From:   syzbot <syzbot+10c98dc5725c6c8fc7fb@...kaller.appspotmail.com>
To:     coreteam@...filter.org, davem@...emloft.net, fw@...len.de,
        kadlec@...ckhole.kfki.hu, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        pablo@...filter.org, syzkaller-bugs@...glegroups.com
Subject: kernel BUG at kernel/time/timer.c:LINE!

Hello,

syzbot hit the following crash on upstream commit
f9f1e414128ea58d8e848a0275db0f644c9e9f45 (Fri Feb 9 18:07:39 2018 +0000)
Merge tag 'for-linus-4.16-rc1-tag' of  
git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

So far this crash happened 9 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+10c98dc5725c6c8fc7fb@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

------------[ cut here ]------------
kernel BUG at kernel/time/timer.c:958!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 1826 Comm: kworker/1:2 Not tainted 4.15.0+ #306
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: ipv6_addrconf addrconf_dad_work
RIP: 0010:__mod_timer kernel/time/timer.c:958 [inline]
RIP: 0010:mod_timer+0x7d6/0x13c0 kernel/time/timer.c:1102
RSP: 0018:ffff8801d24fe9f8 EFLAGS: 00010293
RAX: ffff8801d25246c0 RBX: ffff8801aec6cb50 RCX: ffffffff816052c6
RDX: 0000000000000000 RSI: 00000000fffbd14b RDI: ffff8801aec6cb68
RBP: ffff8801d24fec98 R08: 0000000000000000 R09: 1ffff1003a49fd6c
R10: ffff8801d24feb28 R11: 0000000000000005 R12: dffffc0000000000
R13: ffff8801d24fec70 R14: 00000000fffbd14b R15: ffff8801af608f90
FS:  0000000000000000(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000206d6fd0 CR3: 0000000006a22001 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  led_tg+0x1db/0x2e0 net/netfilter/xt_LED.c:75
  ip6t_do_table+0xc2a/0x1a30 net/ipv6/netfilter/ip6_tables.c:365
  ip6table_raw_hook+0x65/0x80 net/ipv6/netfilter/ip6table_raw.c:42
  nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
  nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
  nf_hook.constprop.27+0x3f6/0x830 include/linux/netfilter.h:243
  NF_HOOK include/linux/netfilter.h:286 [inline]
  ndisc_send_skb+0xa51/0x1370 net/ipv6/ndisc.c:491
  ndisc_send_ns+0x38a/0x870 net/ipv6/ndisc.c:633
  addrconf_dad_work+0xb9e/0x1320 net/ipv6/addrconf.c:4008
  process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:429
Code: 85 2a 0b 00 00 4d 8b 3c 24 4d 85 ff 75 9f 4c 8b bd 60 fd ff ff e8 bb  
57 10 00 65 ff 0d 94 9a a1 7e e9 d9 fc ff ff e8 aa 57 10 00 <0f> 0b e8 a3  
57 10 00 e9 14 fb ff ff e8 99 57 10 00 4c 89 bd 70
RIP: __mod_timer kernel/time/timer.c:958 [inline] RSP: ffff8801d24fe9f8
RIP: mod_timer+0x7d6/0x13c0 kernel/time/timer.c:1102 RSP: ffff8801d24fe9f8
---[ end trace f661ab06f5dd8b3d ]---
Kernel panic - not syncing: Fatal exception in interrupt
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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View attachment "raw.log.txt" of type "text/plain" (9164 bytes)

View attachment "repro.syz.txt" of type "text/plain" (1656 bytes)

View attachment "repro.c.txt" of type "text/plain" (58119 bytes)

View attachment "config.txt" of type "text/plain" (136385 bytes)

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