memory leak in nr_loopback_queue

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    9fb67d64 Merge tag 'pinctrl-v5.2-2' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15956d52a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=64479170dcaf0e11
dashboard link: https://syzkaller.appspot.com/bug?extid=470d1a4a7b7a7c225881
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11bc96a2a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+470d1a4a7b7a7c225881@xxxxxxxxxxxxxxxxxxxxxxxxx

2019/05/29 16:46:11 executed programs: 584
2019/05/29 16:46:19 executed programs: 614
2019/05/29 16:46:26 executed programs: 624
2019/05/29 16:46:33 executed programs: 640
2019/05/29 16:46:41 executed programs: 654
BUG: memory leak
unreferenced object 0xffff888117e5ba00 (size 224):
  comm "syz-executor.2", pid 10957, jiffies 4294999655 (age 10.170s)
  hex dump (first 32 bytes):
    d0 50 cc 17 81 88 ff ff d0 50 cc 17 81 88 ff ff  .P.......P......
    00 00 00 00 00 00 00 00 00 10 b2 08 81 88 ff ff  ................
  backtrace:
    [<00000000af44a575>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:55 [inline]
    [<00000000af44a575>] slab_post_alloc_hook mm/slab.h:439 [inline]
    [<00000000af44a575>] slab_alloc_node mm/slab.c:3269 [inline]
    [<00000000af44a575>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579
    [<000000007d2ff911>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:198
    [<00000000f697bd2b>] alloc_skb include/linux/skbuff.h:1058 [inline]
    [<00000000f697bd2b>] nr_loopback_queue+0x26/0xc0  
net/netrom/nr_loopback.c:37
    [<00000000eb3a969d>] nr_route_frame+0x2d1/0x340  
net/netrom/nr_route.c:775
    [<000000002dad2e7e>] nr_transmit_buffer+0x86/0xc0  
net/netrom/nr_out.c:212
    [<000000006d8f7662>] nr_write_internal+0x133/0x2e0  
net/netrom/nr_subr.c:208
    [<0000000004553967>] nr_establish_data_link+0x2d/0x60  
net/netrom/nr_out.c:230
    [<000000000382326a>] nr_connect+0x13b/0x490 net/netrom/af_netrom.c:716
    [<00000000a27cdfc2>] __sys_connect+0x11d/0x170 net/socket.c:1840
    [<0000000074ede9c3>] __do_sys_connect net/socket.c:1851 [inline]
    [<0000000074ede9c3>] __se_sys_connect net/socket.c:1848 [inline]
    [<0000000074ede9c3>] __x64_sys_connect+0x1e/0x30 net/socket.c:1848
    [<000000000940d4eb>] do_syscall_64+0x76/0x1a0  
arch/x86/entry/common.c:301
    [<00000000307bfe5c>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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