[syzbot] memory leak in xfrm_user_rcv_msg

[syzbot <syzbot+fb347cf82c73a90efcca@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    fd0aa1a4 Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17464aa4300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ec2526c74098317
dashboard link: https://syzkaller.appspot.com/bug?extid=fb347cf82c73a90efcca
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14946548300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10d28548300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fb347cf82c73a90efcca@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff88810f402d00 (size 232):
  comm "syz-executor486", pid 8416, jiffies 4294943639 (age 13.060s)
  hex dump (first 32 bytes):
    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 00 00 00 00 00  ................
  backtrace:
    [<ffffffff836a0d5f>] __alloc_skb+0x20f/0x280 net/core/skbuff.c:413
    [<ffffffff83ad5686>] alloc_skb include/linux/skbuff.h:1107 [inline]
    [<ffffffff83ad5686>] xfrm_alloc_compat+0x1d6/0x6d0 net/xfrm/xfrm_compat.c:324
    [<ffffffff83ad2b4c>] xfrm_alloc_userspi+0x29c/0x3f0 net/xfrm/xfrm_user.c:1448
    [<ffffffff83ace7f8>] xfrm_user_rcv_msg+0x208/0x3e0 net/xfrm/xfrm_user.c:2812
    [<ffffffff838233d7>] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2504
    [<ffffffff83acc9e2>] xfrm_netlink_rcv+0x32/0x40 net/xfrm/xfrm_user.c:2824
    [<ffffffff838225c2>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
    [<ffffffff838225c2>] netlink_unicast+0x392/0x4c0 net/netlink/af_netlink.c:1340
    [<ffffffff83822a58>] netlink_sendmsg+0x368/0x6a0 net/netlink/af_netlink.c:1929
    [<ffffffff836908a6>] sock_sendmsg_nosec net/socket.c:654 [inline]
    [<ffffffff836908a6>] sock_sendmsg+0x56/0x80 net/socket.c:674
    [<ffffffff83696c6f>] sock_no_sendpage+0x8f/0xc0 net/core/sock.c:2862
    [<ffffffff836901ab>] kernel_sendpage.part.0+0xeb/0x150 net/socket.c:3631
    [<ffffffff83690e8b>] kernel_sendpage net/socket.c:3628 [inline]
    [<ffffffff83690e8b>] sock_sendpage+0x5b/0x90 net/socket.c:947
    [<ffffffff815b8872>] pipe_to_sendpage+0xa2/0x110 fs/splice.c:364
    [<ffffffff815ba712>] splice_from_pipe_feed fs/splice.c:418 [inline]
    [<ffffffff815ba712>] __splice_from_pipe+0x1e2/0x330 fs/splice.c:562
    [<ffffffff815baf3f>] splice_from_pipe fs/splice.c:597 [inline]
    [<ffffffff815baf3f>] generic_splice_sendpage+0x6f/0xa0 fs/splice.c:746
    [<ffffffff815b892b>] do_splice_from fs/splice.c:767 [inline]
    [<ffffffff815b892b>] direct_splice_actor+0x4b/0x70 fs/splice.c:936



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