Re: general protection fault in inet_accept

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    fd800f646402 wan/fsl_ucc_hdlc: use IS_ERR_VALUE() to check..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1579b51c400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=acf770f568ef945b
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9616288940d15a6476
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=179e4d62400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f7a978400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e9616288940d15a6476@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: 1 PID: 5524 Comm: kworker/1:120 Not tainted 4.18.0-rc5+ #137
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events smc_tcp_listen_work
RIP: 0010:inet_accept+0xf2/0xa00 net/ipv4/af_inet.c:735
Code: 84 d2 74 09 80 fa 03 0f 8e 95 07 00 00 48 8d 78 28 41 c7 46 80 ea ff  
ff ff 48 ba 00 00 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 <80> 3c 11 00 0f  
85 96 07 00 00 48 b9 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffff8801ce71f4b0 EFLAGS: 00010206
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000005
RDX: dffffc0000000000 RSI: ffffffff8677aa46 RDI: 0000000000000028
RBP: ffff8801ce71f598 R08: ffff8801ae2e8480 R09: ffffed0037e1236f
R10: ffffed0037e1236f R11: ffff8801bf091b7b R12: ffff8801bf091ac0
R13: ffff8801ce71f4f0 R14: ffff8801ce71f570 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200024c0 CR3: 0000000008e6a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 kernel_accept+0x136/0x310 net/socket.c:3251
 smc_clcsock_accept net/smc/af_smc.c:832 [inline]
 smc_tcp_listen_work+0x222/0xef0 net/smc/af_smc.c:1296
 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace de997303bb6ff5f8 ]---
RIP: 0010:inet_accept+0xf2/0xa00 net/ipv4/af_inet.c:735
Code: 84 d2 74 09 80 fa 03 0f 8e 95 07 00 00 48 8d 78 28 41 c7 46 80 ea ff  
ff ff 48 ba 00 00 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 <80> 3c 11 00 0f  
85 96 07 00 00 48 b9 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffff8801ce71f4b0 EFLAGS: 00010206
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000005
RDX: dffffc0000000000 RSI: ffffffff8677aa46 RDI: 0000000000000028
RBP: ffff8801ce71f598 R08: ffff8801ae2e8480 R09: ffffed0037e1236f
R10: ffffed0037e1236f R11: ffff8801bf091b7b R12: ffff8801bf091ac0
R13: ffff8801ce71f4f0 R14: ffff8801ce71f570 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200024c0 CR3: 0000000008e6a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400