general protection fault in send_sigurg_to_task

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    5ed5da74de9e Add linux-next specific files for 20180813
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16c2a63c400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=18edf0289d1b5ab
dashboard link: https://syzkaller.appspot.com/bug?extid=1f371ca19b341a276761
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

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+1f371ca19b341a276761@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 0 PID: 19114 Comm: syz-executor6 Not tainted 4.18.0-next-20180813+ #37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:sigio_perm fs/fcntl.c:715 [inline]
RIP: 0010:send_sigurg_to_task+0xf5/0x4d0 fs/fcntl.c:810
Code: 61 af b1 ff 45 84 f6 0f 84 52 03 00 00 e8 83 ae b1 ff 49 8d bf 58 06  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 91 03 00 00 48 8d 43 c0 4d 8b b7 58 06 00 00 48
RSP: 0018:ffff88019afc74a8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88019afc7518 RCX: ffffc9000643f000
RDX: 00000000000000cb RSI: ffffffff81cadf6d RDI: 0000000000000658
RBP: ffff88019afc7540 R08: ffff8801b16ae5c0 R09: ffffed003b6046d6
R10: ffffed003b6046d6 R11: ffff8801db0236b3 R12: 1ffff100335f8e97
R13: ffff8801cb8ddb48 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f2e92a99700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa4f3c16e18 CR3: 00000001b2e21000 CR4: 00000000001406f0
Call Trace:
 send_sigurg+0x342/0x480 fs/fcntl.c:833
 sk_send_sigurg+0xd2/0x3d0 net/core/sock.c:2731
 tcp_check_urg net/ipv4/tcp_input.c:5266 [inline]
 tcp_urg+0x3c3/0xba0 net/ipv4/tcp_input.c:5307
 tcp_rcv_established+0xd45/0x2130 net/ipv4/tcp_input.c:5637
 tcp_v4_do_rcv+0x635/0x8f0 net/ipv4/tcp_ipv4.c:1532
 sk_backlog_rcv include/net/sock.h:931 [inline]
 __release_sock+0x12f/0x3a0 net/core/sock.c:2336
 release_sock+0xad/0x2c0 net/core/sock.c:2849
 tcp_sendmsg+0x3a/0x50 net/ipv4/tcp.c:1444
 inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:632
 __sys_sendto+0x3d7/0x670 net/socket.c:1787
 __do_sys_sendto net/socket.c:1799 [inline]
 __se_sys_sendto net/socket.c:1795 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1795
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457089
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2e92a98c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f2e92a996d4 RCX: 0000000000457089
RDX: fffffffffffffd43 RSI: 0000000020de1fff RDI: 0000000000000004
RBP: 00000000009300a0 R08: 0000000020db4ff0 R09: 0000000000000010
R10: 0000000020008005 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d3d08 R14: 00000000004c898d R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace dc729739ab19eafd ]---
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:sigio_perm fs/fcntl.c:715 [inline]
RIP: 0010:send_sigurg_to_task+0xf5/0x4d0 fs/fcntl.c:810
Code: 61 af b1 ff 45 84 f6 0f 84 52 03 00 00 e8 83 ae b1 ff 49 8d bf 58 06  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 91 03 00 00 48 8d 43 c0 4d 8b b7 58 06 00 00 48
RSP: 0018:ffff88019afc74a8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88019afc7518 RCX: ffffc9000643f000
RDX: 00000000000000cb RSI: ffffffff81cadf6d RDI: 0000000000000658
RBP: ffff88019afc7540 R08: ffff8801b16ae5c0 R09: ffffed003b6046d6
R10: ffffed003b6046d6 R11: ffff8801db0236b3 R12: 1ffff100335f8e97
R13: ffff8801cb8ddb48 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f2e92a99700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa4f3c16e18 CR3: 00000001b2e21000 CR4: 00000000001406f0


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