general protection fault in __smc_diag_dump

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: bc2bccef Linux 4.14.130
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1323ae7ea00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d6a6b0abab548b75
dashboard link: https://syzkaller.appspot.com/bug?extid=2d2cd56fd53cec16c9ce
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11daedf6a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2d2cd5...@syzkaller.appspotmail.com

SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0
sclass=netlink_tcpdiag_socket pig=7129 comm=syz-executor.0
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0
sclass=netlink_tcpdiag_socket pig=7129 comm=syz-executor.0
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
Modules linked in:
CPU: 0 PID: 7139 Comm: syz-executor.0 Not tainted 4.14.130 #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff88809ba14140 task.stack: ffff888095d18000
RIP: 0010:smc_diag_msg_common_fill net/smc/smc_diag.c:44 [inline]
RIP: 0010:__smc_diag_dump.isra.0+0x342/0x17b0 net/smc/smc_diag.c:82
RSP: 0018:ffff888095d1f340 EFLAGS: 00010203
RAX: dffffc0000000000 RBX: ffff88807d550cc0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000000e
RBP: ffff888095d1f518 R08: 0000000000000040 R09: ffff88807d550d10
R10: ffff88809ba14a60 R11: ffff88809ba14140 R12: ffff888095d1f4f0
R13: ffff8880a1694610 R14: ffff8880865d8040 R15: ffff8880865d8490
FS: 00007ff638990700(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff63896edb8 CR3: 0000000090329000 CR4: 00000000001406f0
Call Trace:
smc_diag_dump+0x1e5/0x2a0 net/smc/smc_diag.c:170
netlink_dump+0x3fa/0xb10 net/netlink/af_netlink.c:2202
__netlink_dump_start+0x4ff/0x750 net/netlink/af_netlink.c:2299
netlink_dump_start include/linux/netlink.h:217 [inline]
smc_diag_handler_dump+0x1b7/0x200 net/smc/smc_diag.c:191
__sock_diag_cmd net/core/sock_diag.c:231 [inline]
sock_diag_rcv_msg+0x29e/0x3a0 net/core/sock_diag.c:263
netlink_rcv_skb+0x14f/0x3c0 net/netlink/af_netlink.c:2432
sock_diag_rcv+0x2b/0x40 net/core/sock_diag.c:274
netlink_unicast_kernel net/netlink/af_netlink.c:1286 [inline]
netlink_unicast+0x45d/0x780 net/netlink/af_netlink.c:1312
netlink_sendmsg+0x7c4/0xc60 net/netlink/af_netlink.c:1877
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xce/0x110 net/socket.c:656
kernel_sendmsg+0x44/0x50 net/socket.c:664
sock_no_sendpage+0x107/0x130 net/core/sock.c:2567
kernel_sendpage+0x92/0xf0 net/socket.c:3415
sock_sendpage+0x8b/0xc0 net/socket.c:871
pipe_to_sendpage+0x242/0x340 fs/splice.c:451
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x348/0x780 fs/splice.c:626
splice_from_pipe+0xf0/0x150 fs/splice.c:661
generic_splice_sendpage+0x3c/0x50 fs/splice.c:832
do_splice_from fs/splice.c:851 [inline]
do_splice fs/splice.c:1147 [inline]
SYSC_splice fs/splice.c:1402 [inline]
SyS_splice+0xd92/0x1430 fs/splice.c:1382
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459519
RSP: 002b:00007ff63898fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000459519
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000075bfc8 R08: 0000000080000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff6389906d4
R13: 00000000004c8a66 R14: 00000000004deb70 R15: 00000000ffffffff
Code: 20 48 89 f9 48 c1 e9 03 80 3c 11 00 0f 85 b2 13 00 00 48 8b 50 20 48
b8 00 00 00 00 00 fc ff df 48 8d 7a 0e 48 89 f9 48 c1 e9 03 <0f> b6 0c 01
48 89 f8 83 e0 07 83 c0 01 38 c8 7c 08 84 c9 0f 85
RIP: smc_diag_msg_common_fill net/smc/smc_diag.c:44 [inline] RSP:
ffff888095d1f340
RIP: __smc_diag_dump.isra.0+0x342/0x17b0 net/smc/smc_diag.c:82 RSP:
ffff888095d1f340
---[ end trace f6daabf12873434c ]---


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