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

From: Santosh Shilimkar
Date: Mon Dec 18 2017 - 11:28:24 EST

On 12/18/2017 12:43 AM, syzbot wrote:

syzkaller hit the following crash on 6084b576dca2e898f5c101baef151f7bfdbb606d
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

Looks like another one tripping on empty transport. Mostly below should
address it but we will test it if it does.

diff --git a/net/rds/send.c b/net/rds/send.c
index 7244d2e..e2d0eaa 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -183,7 +183,7 @@ int rds_send_xmit(struct rds_conn_path *cp)
goto out;

- if (conn->c_trans->xmit_path_prepare)
+ if (conn->c_trans && conn->c_trans->xmit_path_prepare)