netdev - [PATCH net] net/sched: act_pedit: limit negative offset

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Message-Id: <20161127155815.10359-1-amir@vadai.me>
Date:   Sun, 27 Nov 2016 17:58:15 +0200
From:   Amir Vadai <amir@...ai.me>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Hadar Har-Zion <hadarh@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>, Amir Vadai <amir@...ai.me>
Subject: [PATCH net] net/sched: act_pedit: limit negative offset

Should not allow setting a negative offset that goes below the skb head.

Signed-off-by: Amir Vadai <amir@...ai.me>
---
Hi Dave,

Please pull to -stable branches.

Thanks,
Amir

 net/sched/act_pedit.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index b54d56d4959b..e79e8a88f2d2 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -154,8 +154,11 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
 			}
 
 			ptr = skb_header_pointer(skb, off + offset, 4, &_data);
-			if (!ptr)
+			if ((unsigned char *)ptr < skb->head) {
+				pr_info("tc filter pedit offset out of bounds\n");
 				goto bad;
+			}
+
 			/* just do it, baby */
 			*ptr = ((*ptr & tkey->mask) ^ tkey->val);
 			if (ptr == &_data)
-- 
2.10.2