linux-kernel - [PATCH] net: sched: fix a use-after-free error on chain on the error exit path

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Message-Id: <20170518140702.6072-1-colin.king@canonical.com>
Date:   Thu, 18 May 2017 15:07:02 +0100
From:   Colin King <colin.king@...onical.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] net: sched: fix a use-after-free error on chain on the error exit path

From: Colin Ian King <colin.king@...onical.com>

Set chain to null after the call to tcf_chain_destroy so that we don't
call tcf_chain_put on the error exit path, thus avoiding a use-after-free
error.

Detected by CoverityScan, CID#1436357 ("Use after free")

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/sched/cls_api.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 4020b8d932a1..82ebdc3fcb2e 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -511,6 +511,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	if (n->nlmsg_type == RTM_DELTFILTER && prio == 0) {
 		tfilter_notify_chain(net, skb, n, chain, RTM_DELTFILTER);
 		tcf_chain_destroy(chain);
+		chain = NULL;
 		err = 0;
 		goto errout;
 	}
-- 
2.11.0