WARNING in strp_done

Hello,

syzbot hit the following crash on upstream commit
5b7d27967dabfb17c21b0d98b29153b9e3ee71e5 (Thu Jan 25 01:24:30 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

So far this crash happened 1937 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.

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Reported-by: syzbot+88dfb55e4c8b770d86e3@syzkaller.appspotmail.com
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WARNING: CPU: 1 PID: 3786 at net/strparser/strparser.c:532  
strp_done+0xb7/0xe0 net/strparser/strparser.c:532
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3786 Comm: syzkaller868787 Not tainted 4.15.0-rc9+ #279
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  panic+0x1e4/0x41c kernel/panic.c:183
  __warn+0x1dc/0x200 kernel/panic.c:547
  report_bug+0x211/0x2d0 lib/bug.c:184
  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
  fixup_bug arch/x86/kernel/traps.c:247 [inline]
  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
  invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1096
RIP: 0010:strp_done+0xb7/0xe0 net/strparser/strparser.c:532
RSP: 0018:ffff8801d875fac0 EFLAGS: 00010293
RAX: ffff8801d0850680 RBX: ffff8801bbd89908 RCX: ffffffff84fdc797
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801bbd89910
RBP: ffff8801d875fad8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801bac92a00
R13: ffffc90000002000 R14: ffff8801bec88040 R15: ffff8801d875fcd8
  kcm_attach net/kcm/kcmsock.c:1420 [inline]
  kcm_attach_ioctl net/kcm/kcmsock.c:1477 [inline]
  kcm_ioctl+0x139a/0x17f0 net/kcm/kcmsock.c:1682
  sock_do_ioctl+0x65/0xb0 net/socket.c:966
  sock_ioctl+0x2c2/0x440 net/socket.c:1063
  vfs_ioctl fs/ioctl.c:46 [inline]
  do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
  SYSC_ioctl fs/ioctl.c:701 [inline]
  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
  entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x44aba9
RSP: 002b:00007fa1da5c0d48 EFLAGS: 00000297 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dcc3c RCX: 000000000044aba9
RDX: 0000000020ed6ff8 RSI: 00000000000089e0 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dcc38
R13: 656c6c616b7a7973 R14: 00007fa1da5c19c0 R15: 0000000000002710
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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