netdev - [Patch net] kcm: fix a null pointer dereference in kcm

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Message-Id: <1487013196-2375-1-git-send-email-xiyou.wangcong@gmail.com>
Date:   Mon, 13 Feb 2017 11:13:16 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     dvyukov@...gle.com, Cong Wang <xiyou.wangcong@...il.com>,
        Tom Herbert <tom@...bertland.com>
Subject: [Patch net] kcm: fix a null pointer dereference in kcm_sendmsg()

In commit 98e3862ca2b1 ("kcm: fix 0-length case for kcm_sendmsg()")
I tried to avoid skb allocation for 0-length case, but missed
a check for NULL pointer in the non EOR case.

Fixes: 98e3862ca2b1 ("kcm: fix 0-length case for kcm_sendmsg()")
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Tom Herbert <tom@...bertland.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 net/kcm/kcmsock.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 64f0e85..a646f34 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1044,8 +1044,10 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	} else {
 		/* Message not complete, save state */
 partial_message:
-		kcm->seq_skb = head;
-		kcm_tx_msg(head)->last_skb = skb;
+		if (head) {
+			kcm->seq_skb = head;
+			kcm_tx_msg(head)->last_skb = skb;
+		}
 	}
 
 	KCM_STATS_ADD(kcm->stats.tx_bytes, copied);
-- 
2.5.5