general protection fault in rxrpc_send_keepalive

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 38b9e0f6 Merge tag 'mlx5-updates-2019-08-09' of git://git...
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1316aa6a600000
kernel config: https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
dashboard link: https://syzkaller.appspot.com/bug?extid=345e0797ca47ec984348
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [da...@davemloft.net dhow...@redhat.com
linu...@lists.infradead.org linux-...@vger.kernel.org
net...@vger.kernel.org net...@vger.kernel.org]

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+345e07...@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: 31535 Comm: kworker/0:1 Not tainted 5.3.0-rc3+ #126
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
RIP: 0010:rxrpc_send_keepalive+0x14f/0x940 net/rxrpc/output.c:635
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 67 07 00 00 48 b8 00 00 00 00
00 fc ff df 4d 8b 6e 18 49 8d 7d 08 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84
c0 74 08 3c 03 0f 8e c9 06 00 00 41 8b 45 08 49 8d
RSP: 0018:ffff88805f867ab0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff88808eccf680 RCX: ffffffff869c5dee
RDX: 0000000020008a93 RSI: ffffffff869c2e12 RDI: 0000000100045498
RBP: ffff88805f867c28 R08: ffff888094156240 R09: ffffed1013bcd502
R10: ffffed1013bcd501 R11: ffff88809de6a80b R12: 0000000000000014
R13: 0000000100045490 R14: ffff8880927cd6c0 R15: 0000000000000c8e
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7457a70000 CR3: 000000006104c000 CR4: 00000000001406f0
Call Trace:
rxrpc_peer_keepalive_dispatch net/rxrpc/peer_event.c:369 [inline]
rxrpc_peer_keepalive_worker+0x7be/0xd02 net/rxrpc/peer_event.c:430
process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 6562d76764a11822 ]---
RIP: 0010:rxrpc_send_keepalive+0x14f/0x940 net/rxrpc/output.c:635
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 67 07 00 00 48 b8 00 00 00 00
00 fc ff df 4d 8b 6e 18 49 8d 7d 08 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84
c0 74 08 3c 03 0f 8e c9 06 00 00 41 8b 45 08 49 8d
RSP: 0018:ffff88805f867ab0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff88808eccf680 RCX: ffffffff869c5dee
RDX: 0000000020008a93 RSI: ffffffff869c2e12 RDI: 0000000100045498
RBP: ffff88805f867c28 R08: ffff888094156240 R09: ffffed1013bcd502
R10: ffffed1013bcd501 R11: ffff88809de6a80b R12: 0000000000000014
R13: 0000000100045490 R14: ffff8880927cd6c0 R15: 0000000000000c8e
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000000a8789000 CR4: 00000000001406f0


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