Subject: BUG: unable to handle kernel NULL pointer dereference in rds_send_xmit

From: syzbot <[email-masked]>
Date: Mon, 18 Dec 2017 00:43:01 -0800

Hello,

syzkaller hit the following crash on  
6084b576dca2e898f5c101baef151f7bfdbb606d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
program syz-executor6 is using a deprecated SCSI ioctl, please convert it  
to SG_IO
IP: rds_send_xmit+0x80/0x930 net/rds/send.c:186
PGD 20e367067 P4D 20e367067 PUD 2118c1067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4514 Comm: kworker/u4:4 Not tainted 4.15.0-rc3-next-20171214+  
#67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krdsd rds_send_worker
RIP: 0010:rds_send_xmit+0x80/0x930 net/rds/send.c:186
RSP: 0018:ffffc90000f6fdc0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88020e3234c0 RCX: ffffffff8241b25c
RDX: 0000000000000000 RSI: ffffffff83080700 RDI: ffff88020e323400
RBP: ffffc90000f6fe28 R08: 0000000000000001 R09: 0000000000000004
R10: ffffc90000f6fde0 R11: 0000000000000004 R12: ffff88020e3234c0
R13: ffff88020e323400 R14: ffff88021780d800 R15: ffff8802150fc600
FS:  0000000000000000(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000028 CR3: 00000002119da000 CR4: 00000000001406f0
DR0: 0000000020000000 DR1: 0000000020001008 DR2: 0000000020001010
DR3: 0000000020000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
  rds_send_worker+0x37/0x100 net/rds/threads.c:189
  process_one_work+0x288/0x7a0 kernel/workqueue.c:2112
  worker_thread+0x43/0x4d0 kernel/workqueue.c:2246
  kthread+0x149/0x170 kernel/kthread.c:238
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Code: 00 00 00 48 83 c0 01 48 89 45 a0 49 89 85 a8 00 00 00 41 8b 85 a0 00  
00 00 83 f8 03 0f 85 4f 08 00 00 e8 e4 f0 e9 fe 48 8b 45 b8 <48> 8b 40 28  
48 8b 58 58 48 85 db 74 0a e8 ce f0 e9 fe 4c 89 ef
RIP: rds_send_xmit+0x80/0x930 net/rds/send.c:186 RSP: ffffc90000f6fdc0
CR2: 0000000000000028
---[ end trace 1bd85784f8eb115b ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

---
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