memory leak in rawv6_sendmsg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    c50bbf61 Merge tag 'platform-drivers-x86-v5.2-2' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e86bf8a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=61dd9e15a761691d
dashboard link: https://syzkaller.appspot.com/bug?extid=0210b383c62bb2a35e32
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=131e5c9aa00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14092dbca00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0210b383c62bb2a35e32@xxxxxxxxxxxxxxxxxxxxxxxxx

ed '10.128.1.53' (ECDSA) to the list of known hosts.
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff8881099cc500 (size 224):
  comm "syz-executor618", pid 7230, jiffies 4294944637 (age 13.010s)
  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:
    [<00000000dc438dab>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:55 [inline]
    [<00000000dc438dab>] slab_post_alloc_hook mm/slab.h:439 [inline]
    [<00000000dc438dab>] slab_alloc_node mm/slab.c:3269 [inline]
    [<00000000dc438dab>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579
    [<00000000fdd6976f>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:198
    [<000000007051ec41>] alloc_skb include/linux/skbuff.h:1058 [inline]
    [<000000007051ec41>] alloc_skb_with_frags+0x5f/0x250  
net/core/skbuff.c:5327
    [<00000000ff05b767>] sock_alloc_send_pskb+0x269/0x2a0  
net/core/sock.c:2225
    [<0000000007cd012b>] sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2242
    [<00000000e26691f9>] rawv6_send_hdrinc net/ipv6/raw.c:644 [inline]
    [<00000000e26691f9>] rawv6_sendmsg+0x9c9/0x12f0 net/ipv6/raw.c:935
    [<000000003e27012a>] inet_sendmsg+0x64/0x120 net/ipv4/af_inet.c:802
    [<000000005750e5ca>] sock_sendmsg_nosec net/socket.c:652 [inline]
    [<000000005750e5ca>] sock_sendmsg+0x54/0x70 net/socket.c:671
    [<000000002a4faea6>] ___sys_sendmsg+0x393/0x3c0 net/socket.c:2292
    [<00000000aee219ed>] __sys_sendmsg+0x80/0xf0 net/socket.c:2330
    [<00000000d1f2b00e>] __do_sys_sendmsg net/socket.c:2339 [inline]
    [<00000000d1f2b00e>] __se_sys_sendmsg net/socket.c:2337 [inline]
    [<00000000d1f2b00e>] __x64_sys_sendmsg+0x23/0x30 net/socket.c:2337
    [<00000000388062fd>] do_syscall_64+0x76/0x1a0  
arch/x86/entry/common.c:301
    [<000000009c436e23>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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