memory leak in mrp_request_join

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    d96d875e Merge tag 'fixes_for_v5.5-rc8' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14cd8185e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=15478c61c836a72e
dashboard link: https://syzkaller.appspot.com/bug?extid=5cfab121b54dff775399
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14dbe201e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13e03cf1e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5cfab121b54dff775399@xxxxxxxxxxxxxxxxxxxxxxxxx

executing program
BUG: memory leak
unreferenced object 0xffff888120b85c40 (size 64):
  comm "syz-executor783", pid 7302, jiffies 4294942613 (age 14.030s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 01 00 00 00 01 02 00 00  ................
  backtrace:
    [<000000000312cb0f>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline]
    [<000000000312cb0f>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<000000000312cb0f>] slab_alloc mm/slab.c:3320 [inline]
    [<000000000312cb0f>] __do_kmalloc mm/slab.c:3654 [inline]
    [<000000000312cb0f>] __kmalloc+0x169/0x300 mm/slab.c:3665
    [<0000000011736472>] kmalloc include/linux/slab.h:561 [inline]
    [<0000000011736472>] mrp_attr_create net/802/mrp.c:276 [inline]
    [<0000000011736472>] mrp_request_join+0x13d/0x220 net/802/mrp.c:530
    [<000000003ff9bf8f>] vlan_mvrp_request_join+0x86/0x90 net/8021q/vlan_mvrp.c:40
    [<0000000020a13a26>] vlan_dev_open+0x154/0x290 net/8021q/vlan_dev.c:293
    [<0000000010d96d5d>] __dev_open+0x109/0x1b0 net/core/dev.c:1431
    [<00000000e9578876>] __dev_change_flags+0x246/0x2c0 net/core/dev.c:8103
    [<000000002c92e0e1>] rtnl_configure_link+0x57/0x100 net/core/rtnetlink.c:2996
    [<000000000504898e>] __rtnl_newlink+0x8b9/0xb80 net/core/rtnetlink.c:3323
    [<00000000eb645fa3>] rtnl_newlink+0x4e/0x80 net/core/rtnetlink.c:3363
    [<0000000034f28a5d>] rtnetlink_rcv_msg+0x178/0x4b0 net/core/rtnetlink.c:5424
    [<00000000dc499e73>] netlink_rcv_skb+0x61/0x170 net/netlink/af_netlink.c:2477
    [<00000000b6cd4d73>] rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5442
    [<0000000092a30a6a>] netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
    [<0000000092a30a6a>] netlink_unicast+0x223/0x310 net/netlink/af_netlink.c:1328
    [<0000000006ceb85b>] netlink_sendmsg+0x2c0/0x570 net/netlink/af_netlink.c:1917
    [<000000009199ec36>] sock_sendmsg_nosec net/socket.c:639 [inline]
    [<000000009199ec36>] sock_sendmsg+0x54/0x70 net/socket.c:659
    [<000000002acd085e>] ____sys_sendmsg+0x2d0/0x300 net/socket.c:2330



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