WARNING: refcount bug in sk_alloc

[syzbot]

Hello,

syzbot hit the following crash on bpf-next commit
6f1b5a2b58d8470e5a8b25ab29f5fdb4616ffff8 (Tue Feb 27 04:11:23 2018 +0000)
Merge branch 'bpf-kselftest-improvements'

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
CC: [da...@davemloft.net kuz...@ms2.inr.ac.ru linux-...@vger.kernel.org
net...@vger.kernel.org yosh...@linux-ipv6.org]

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Reported-by: syzbot+0f1f24...@syzkaller.appspotmail.com
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------------[ cut here ]------------
refcount_t: increment on 0; use-after-free.
WARNING: CPU: 1 PID: 10759 at lib/refcount.c:153 refcount_inc+0x47/0x50
lib/refcount.c:153
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 10759 Comm: syz-executor5 Not tainted 4.16.0-rc2+ #20
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+0x194/0x24d 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+0x58/0x80 arch/x86/entry/entry_64.S:957
RIP: 0010:refcount_inc+0x47/0x50 lib/refcount.c:153
RSP: 0018:ffff8801ad827860 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff8801d2d80304 RCX: ffffffff815ac30e
RDX: 0000000000000000 RSI: 1ffff10035b04ebc RDI: 1ffff10035b04e91
RBP: ffff8801ad827868 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ad827af8
R13: ffff8801da576a93 R14: ffff8801d2d80300 R15: ffff8801da576b01
get_net include/net/net_namespace.h:202 [inline]
sk_alloc+0x3f9/0x1440 net/core/sock.c:1541
inet_create+0x47c/0xf50 net/ipv4/af_inet.c:320
__sock_create+0x4d4/0x850 net/socket.c:1285
sock_create net/socket.c:1325 [inline]
SYSC_socket net/socket.c:1355 [inline]
SyS_socket+0xeb/0x1d0 net/socket.c:1335
do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x456877
RSP: 002b:00007ffd8376b3c8 EFLAGS: 00000202 ORIG_RAX: 0000000000000029
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000456877
RDX: 0000000000000006 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 00007ffd8376ba80 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000005 R11: 0000000000000202 R12: 0000000000000004
R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000f0a914
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Dmitry Vyukov]

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