memory leak in nf_tables_parse_netdev_hooks

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    51d69817 Merge tag 'platform-drivers-x86-v5.5-3' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e32659e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a0eee3ce463efd
dashboard link: https://syzkaller.appspot.com/bug?extid=f9d4095107fc8749c69c
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16fae421e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e41c76e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f9d4095107fc8749c69c@xxxxxxxxxxxxxxxxxxxxxxxxx

executing program
BUG: memory leak
unreferenced object 0xffff8881292d4580 (size 96):
  comm "syz-executor052", pid 7129, jiffies 4294942632 (age 13.530s)
  hex dump (first 32 bytes):
    40 d2 15 1c 81 88 ff ff 40 d2 15 1c 81 88 ff ff  @.......@.......
    60 53 c3 82 ff ff ff ff 00 a0 2c 2a 81 88 ff ff  `S........,*....
  backtrace:
    [<0000000059912bf5>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:43 [inline]
    [<0000000059912bf5>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<0000000059912bf5>] slab_alloc mm/slab.c:3320 [inline]
    [<0000000059912bf5>] kmem_cache_alloc_trace+0x145/0x2c0 mm/slab.c:3549
    [<00000000ab9f7d85>] kmalloc include/linux/slab.h:556 [inline]
    [<00000000ab9f7d85>] nft_netdev_hook_alloc+0x3f/0xd0  
net/netfilter/nf_tables_api.c:1624
    [<0000000074e6bb65>] nf_tables_parse_netdev_hooks+0xac/0x230  
net/netfilter/nf_tables_api.c:1673
    [<00000000cd387efd>] nf_tables_flowtable_parse_hook  
net/netfilter/nf_tables_api.c:5936 [inline]
    [<00000000cd387efd>] nf_tables_newflowtable+0x41e/0x930  
net/netfilter/nf_tables_api.c:6137
    [<00000000526e3994>] nfnetlink_rcv_batch+0x662/0x8c0  
net/netfilter/nfnetlink.c:433
    [<000000006c5402bf>] nfnetlink_rcv_skb_batch  
net/netfilter/nfnetlink.c:543 [inline]
    [<000000006c5402bf>] nfnetlink_rcv+0x189/0x1c0  
net/netfilter/nfnetlink.c:561
    [<00000000b752f9f7>] netlink_unicast_kernel  
net/netlink/af_netlink.c:1302 [inline]
    [<00000000b752f9f7>] netlink_unicast+0x223/0x310  
net/netlink/af_netlink.c:1328
    [<00000000a0e23793>] netlink_sendmsg+0x2c0/0x570  
net/netlink/af_netlink.c:1917
    [<000000006e0aea94>] sock_sendmsg_nosec net/socket.c:639 [inline]
    [<000000006e0aea94>] sock_sendmsg+0x54/0x70 net/socket.c:659
    [<00000000a60c26dd>] ____sys_sendmsg+0x2d0/0x300 net/socket.c:2330
    [<00000000d412f616>] ___sys_sendmsg+0x8a/0xd0 net/socket.c:2384
    [<000000001179a6b0>] __sys_sendmsg+0x80/0xf0 net/socket.c:2417
    [<000000004a6699d1>] __do_sys_sendmsg net/socket.c:2426 [inline]
    [<000000004a6699d1>] __se_sys_sendmsg net/socket.c:2424 [inline]
    [<000000004a6699d1>] __x64_sys_sendmsg+0x23/0x30 net/socket.c:2424
    [<00000000a05aa7d1>] do_syscall_64+0x73/0x220  
arch/x86/entry/common.c:294
    [<00000000bad17b52>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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