general protection fault in smack_socket_sendmsg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6525771f Merge tag 'arc-5.3-rc7' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11486cea600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=58485246ad14eafe
dashboard link: https://syzkaller.appspot.com/bug?extid=5fd781d646d4fcbdfeb0
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5fd781d646d4fcbdfeb0 at syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 11983 Comm: kworker/0:0 Not tainted 5.3.0-rc6+ #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
RIP: 0010:smack_socket_sendmsg+0x5b/0x480 security/smack/smack_lsm.c:3677
Code: e8 6a 07 71 fe 4c 89 e8 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 ef e8  
b4 ff a9 fe 4d 8b 65 00 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00  
74 08 48 89 df e8 96 ff a9 fe 4c 8b 33 49 8d 9e 08
RSP: 0018:ffff8881daa1f9c8 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888048882500
RDX: 0000000000000000 RSI: ffff8881daa1fb18 RDI: 0000000000000000
RBP: ffff8881daa1fa80 R08: ffffffff8350cc90 R09: ffff8881daa1fb86
R10: ffffed103b543f72 R11: 0000000000000000 R12: ffff88803704c594
R13: ffff8881daa1fb18 R14: dffffc0000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7d4f2b5028 CR3: 000000005e835000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  security_socket_sendmsg+0x6c/0xd0 security/security.c:1973
  sock_sendmsg net/socket.c:654 [inline]
  kernel_sendmsg+0x77/0x140 net/socket.c:677
  rxrpc_send_keepalive+0x254/0x3c0 net/rxrpc/output.c:655
  rxrpc_peer_keepalive_dispatch net/rxrpc/peer_event.c:369 [inline]
  rxrpc_peer_keepalive_worker+0x76e/0xb40 net/rxrpc/peer_event.c:430
  process_one_work+0x7ef/0x10e0 kernel/workqueue.c:2269
  worker_thread+0xc01/0x1630 kernel/workqueue.c:2415
  kthread+0x332/0x350 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 61235a384085b26a ]---
RIP: 0010:smack_socket_sendmsg+0x5b/0x480 security/smack/smack_lsm.c:3677
Code: e8 6a 07 71 fe 4c 89 e8 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 ef e8  
b4 ff a9 fe 4d 8b 65 00 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00  
74 08 48 89 df e8 96 ff a9 fe 4c 8b 33 49 8d 9e 08
RSP: 0018:ffff8881daa1f9c8 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff888048882500
RDX: 0000000000000000 RSI: ffff8881daa1fb18 RDI: 0000000000000000
RBP: ffff8881daa1fa80 R08: ffffffff8350cc90 R09: ffff8881daa1fb86
R10: ffffed103b543f72 R11: 0000000000000000 R12: ffff88803704c594
R13: ffff8881daa1fb18 R14: dffffc0000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000960004 CR3: 0000000022fd0000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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