memory leak in ctnetlink_del_conntrack

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10fcd90e100000
kernel config: https://syzkaller.appspot.com/x/.config?x=9a1aa05456dfd557
dashboard link: https://syzkaller.appspot.com/bug?extid=38b8b548a851a01793c5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=129c54c1100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11c0355a100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+38b8b5...@syzkaller.appspotmail.com

executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff88811c505300 (size 128):
comm "syz-executor470", pid 6431, jiffies 4294945909 (age 13.210s)
hex dump (first 32 bytes):
00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000da2809df>] kmalloc include/linux/slab.h:555 [inline]
[<00000000da2809df>] kzalloc include/linux/slab.h:669 [inline]
[<00000000da2809df>] ctnetlink_alloc_filter+0x3a/0x2a0 net/netfilter/nf_conntrack_netlink.c:924
[<00000000745f0fc9>] ctnetlink_flush_conntrack net/netfilter/nf_conntrack_netlink.c:1516 [inline]
[<00000000745f0fc9>] ctnetlink_del_conntrack+0x20a/0x326 net/netfilter/nf_conntrack_netlink.c:1554
[<00000000385a38da>] nfnetlink_rcv_msg+0x32f/0x370 net/netfilter/nfnetlink.c:229
[<00000000bb3b1fc1>] netlink_rcv_skb+0x5a/0x180 net/netlink/af_netlink.c:2469
[<00000000b2799dbb>] nfnetlink_rcv+0x83/0x1b0 net/netfilter/nfnetlink.c:563
[<000000006021f56a>] netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
[<000000006021f56a>] netlink_unicast+0x20a/0x2f0 net/netlink/af_netlink.c:1329
[<000000003a4cd173>] netlink_sendmsg+0x2b5/0x560 net/netlink/af_netlink.c:1918
[<00000000ff287393>] sock_sendmsg_nosec net/socket.c:652 [inline]
[<00000000ff287393>] sock_sendmsg+0x4c/0x60 net/socket.c:672
[<000000008c32b330>] ____sys_sendmsg+0x2c4/0x2f0 net/socket.c:2352
[<00000000a8f57b1b>] ___sys_sendmsg+0x8a/0xd0 net/socket.c:2406
[<000000002c938bcf>] __sys_sendmsg+0x77/0xe0 net/socket.c:2439
[<00000000878f0bd0>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
[<00000000dcd0e014>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff88811ac32a00 (size 128):
comm "syz-executor470", pid 6432, jiffies 4294946459 (age 7.710s)
hex dump (first 32 bytes):
00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000da2809df>] kmalloc include/linux/slab.h:555 [inline]
[<00000000da2809df>] kzalloc include/linux/slab.h:669 [inline]
[<00000000da2809df>] ctnetlink_alloc_filter+0x3a/0x2a0 net/netfilter/nf_conntrack_netlink.c:924
[<00000000745f0fc9>] ctnetlink_flush_conntrack net/netfilter/nf_conntrack_netlink.c:1516 [inline]
[<00000000745f0fc9>] ctnetlink_del_conntrack+0x20a/0x326 net/netfilter/nf_conntrack_netlink.c:1554
[<00000000385a38da>] nfnetlink_rcv_msg+0x32f/0x370 net/netfilter/nfnetlink.c:229
[<00000000bb3b1fc1>] netlink_rcv_skb+0x5a/0x180 net/netlink/af_netlink.c:2469
[<00000000b2799dbb>] nfnetlink_rcv+0x83/0x1b0 net/netfilter/nfnetlink.c:563
[<000000006021f56a>] netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
[<000000006021f56a>] netlink_unicast+0x20a/0x2f0 net/netlink/af_netlink.c:1329
[<000000003a4cd173>] netlink_sendmsg+0x2b5/0x560 net/netlink/af_netlink.c:1918
[<00000000ff287393>] sock_sendmsg_nosec net/socket.c:652 [inline]
[<00000000ff287393>] sock_sendmsg+0x4c/0x60 net/socket.c:672
[<000000008c32b330>] ____sys_sendmsg+0x2c4/0x2f0 net/socket.c:2352
[<00000000a8f57b1b>] ___sys_sendmsg+0x8a/0xd0 net/socket.c:2406
[<000000002c938bcf>] __sys_sendmsg+0x77/0xe0 net/socket.c:2439
[<00000000878f0bd0>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
[<00000000dcd0e014>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches