WARNING: refcount bug in igmp_start_timer

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 815e34f8 Merge 4.14.90 into android-4.14
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=11c348c3400000
kernel config: https://syzkaller.appspot.com/x/.config?x=608dc5a2664d6079
dashboard link: https://syzkaller.appspot.com/bug?extid=16a6a85f154646aea2f9
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10d7a9cd400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+16a6a8...@syzkaller.appspotmail.com

refcount_t: increment on 0; use-after-free.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 31226 at lib/refcount.c:153
refcount_inc.cold.12+0x18/0x1f lib/refcount.c:153
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 31226 Comm: syz-executor0 Not tainted 4.14.90+ #29
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x11b lib/dump_stack.c:53
panic+0x1bf/0x3a4 kernel/panic.c:181
__warn.cold.7+0x2f/0x35 kernel/panic.c:542
report_bug+0x1f7/0x26c lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:177 [inline]
do_error_trap+0x1ba/0x2c0 arch/x86/kernel/traps.c:295
invalid_op+0x18/0x40 arch/x86/entry/entry_64.S:944
RIP: 0010:refcount_inc.cold.12+0x18/0x1f lib/refcount.c:153
RSP: 0018:ffff8881cce5f150 EFLAGS: 00010286
RAX: 000000000000002b RBX: ffff8881d4ff4814 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff94a6aa20 RDI: ffffffff965d8560
RBP: 00000000000003e8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8881d4ff4780 R14: 0000000000000000 R15: ffff8881ca508062
igmp_start_timer+0x98/0xc0 net/ipv4/igmp.c:217
igmp_mod_timer net/ipv4/igmp.c:255 [inline]
igmp_heard_query net/ipv4/igmp.c:1027 [inline]
igmp_rcv+0x1346/0x2400 net/ipv4/igmp.c:1062
ip_local_deliver_finish+0x3f1/0xaa0 net/ipv4/ip_input.c:216
NF_HOOK include/linux/netfilter.h:250 [inline]
ip_local_deliver+0x374/0x450 net/ipv4/ip_input.c:257
dst_input include/net/dst.h:465 [inline]
ip_rcv_finish+0x5cc/0x1490 net/ipv4/ip_input.c:397
NF_HOOK include/linux/netfilter.h:250 [inline]
ip_rcv+0xa19/0x1028 net/ipv4/ip_input.c:493
__netif_receive_skb_core+0x149d/0x2d10 net/core/dev.c:4477
__netif_receive_skb+0x58/0x1f0 net/core/dev.c:4515
netif_receive_skb_internal+0xfc/0x5e0 net/core/dev.c:4588
tun_rx_batched.isra.12+0x464/0x710 drivers/net/tun.c:1218
tun_get_user+0x11d1/0x3c90 drivers/net/tun.c:1570
tun_chr_write_iter+0xcf/0x180 drivers/net/tun.c:1596
call_write_iter include/linux/fs.h:1784 [inline]
do_iter_readv_writev+0x3a4/0x560 fs/read_write.c:678
do_iter_write+0x156/0x530 fs/read_write.c:957
vfs_writev+0x146/0x2d0 fs/read_write.c:1002
do_writev+0xcc/0x240 fs/read_write.c:1037
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457521
RSP: 002b:00007f6a2b384ba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000000002a RCX: 0000000000457521
RDX: 0000000000000001 RSI: 00007f6a2b384bf0 RDI: 00000000000000f0
RBP: 0000000020000640 R08: 00000000000000f0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00007f6a2b3856d4
R13: 00000000004c53b4 R14: 00000000004d9900 R15: 00000000ffffffff
Kernel Offset: 0x11c00000 from 0xffffffff81000000 (relocation range:
0xffffffff80000000-0xffffffffbfffffff)
Rebooting in 86400 seconds..


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