linux-kernel - [PATCH 4.4 10/21] net: sched: Fix a possible null-pointer dereference in dequeue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190809134242.004869565@linuxfoundation.org>
Date:   Fri,  9 Aug 2019 15:45:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 10/21] net: sched: Fix a possible null-pointer dereference in dequeue_func()

From: Jia-Ju Bai <baijiaju1990@...il.com>

[ Upstream commit 051c7b39be4a91f6b7d8c4548444e4b850f1f56c ]

In dequeue_func(), there is an if statement on line 74 to check whether
skb is NULL:
    if (skb)

When skb is NULL, it is used on line 77:
    prefetch(&skb->end);

Thus, a possible null-pointer dereference may occur.

To fix this bug, skb->end is used when skb is not NULL.

This bug is found by a static analysis tool STCheck written by us.

Fixes: 76e3cc126bb2 ("codel: Controlled Delay AQM")
Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
Reviewed-by: Jiri Pirko <jiri@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_codel.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -68,7 +68,8 @@ static struct sk_buff *dequeue(struct co
 {
 	struct sk_buff *skb = __skb_dequeue(&sch->q);
 
-	prefetch(&skb->end); /* we'll need skb_shinfo() */
+	if (skb)
+		prefetch(&skb->end); /* we'll need skb_shinfo() */
 	return skb;
 }