Subject: BUG: unable to handle kernel NULL pointer dereference in addrconf_notify

From: syzbot <[email-masked]>
Date: Tue, 19 Dec 2017 11:48:01 -0800

Hello,

syzkaller hit the following crash on  
6084b576dca2e898f5c101baef151f7bfdbb606d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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

ALSA: seq fatal error: cannot create timer (-22)
device syz2 entered promiscuous mode
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: addrconf_permanent_addr net/ipv6/addrconf.c:3351 [inline]
IP: addrconf_notify+0x7df/0xd50 net/ipv6/addrconf.c:3422
PGD 1fad11067 P4D 1fad11067 PUD 1fad7a067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 15171 Comm: syz-executor2 Not tainted 4.15.0-rc3-next-20171214+  
#67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:addrconf_permanent_addr net/ipv6/addrconf.c:3351 [inline]
RIP: 0010:addrconf_notify+0x7df/0xd50 net/ipv6/addrconf.c:3422
RSP: 0018:ffffc90000d63b80 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff8801fa41a000 RCX: ffff8801faddd808
RDX: 00000000000000ff RSI: 000000002811d9a2 RDI: ffff8801faddd968
RBP: ffffc90000d63c00 R08: 0000000000000001 R09: 0000000000000004
R10: ffffc90000d63af0 R11: 0000000000000004 R12: 0000000000000001
R13: ffff8801faddd800 R14: 0000000000000000 R15: ffff8801faddd800
FS:  00007f4373896700(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000002143c4001 CR4: 00000000001606f0
DR0: 0000000020000008 DR1: 0000000020000000 DR2: 0000000020000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
  notifier_call_chain+0x41/0xc0 kernel/notifier.c:93
  __raw_notifier_call_chain kernel/notifier.c:394 [inline]
  raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
  call_netdevice_notifiers_info+0x32/0x60 net/core/dev.c:1679
  call_netdevice_notifiers net/core/dev.c:1697 [inline]
  __dev_notify_flags+0x75/0x130 net/core/dev.c:6874
  dev_change_flags+0x5e/0x70 net/core/dev.c:6910
  devinet_ioctl+0x77b/0x930 net/ipv4/devinet.c:1083
  inet_ioctl+0xda/0x130 net/ipv4/af_inet.c:902
  sock_do_ioctl+0x2c/0x60 net/socket.c:964
  sock_ioctl+0x211/0x320 net/socket.c:1061
  vfs_ioctl fs/ioctl.c:46 [inline]
  do_vfs_ioctl+0xaf/0x840 fs/ioctl.c:686
  SYSC_ioctl fs/ioctl.c:701 [inline]
  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452a09
RSP: 002b:00007f4373895c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452a09
RDX: 000000002062ffe0 RSI: 0000000000008914 RDI: 0000000000000013
RBP: 00000000000002eb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f16a8
R13: 00000000ffffffff R14: 00007f43738966d4 R15: 0000000000000000
Code: 85 ed 0f 84 f4 00 00 00 e8 ff 3a 06 ff 49 8d 85 68 01 00 00 48 89 c7  
48 89 45 a8 e8 0c 9f 37 00 49 8b 45 08 4c 89 e9 48 83 c1 08 <48> 8b 38 48  
39 c1 4c 8d a8 c8 fe ff ff 4c 8d a7 c8 fe ff ff 0f
RIP: addrconf_permanent_addr net/ipv6/addrconf.c:3351 [inline] RSP:  
ffffc90000d63b80
RIP: addrconf_notify+0x7df/0xd50 net/ipv6/addrconf.c:3422 RSP:  
ffffc90000d63b80
CR2: 0000000000000000
---[ end trace ebbf2e3971cab1b5 ]---

---
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