Patch "net/sched: pedit: make sure that offset is valid" has been added to the 4.8-stable tree

Patch "net/sched: pedit: make sure that offset is valid" has been added to the 4.8-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    net/sched: pedit: make sure that offset is valid

to the 4.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-sched-pedit-make-sure-that-offset-is-valid.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Dec  8 07:19:12 CET 2016
From: Amir Vadai <amir@vadai.me>
Date: Mon, 28 Nov 2016 12:56:40 +0200
Subject: net/sched: pedit: make sure that offset is valid

From: Amir Vadai <amir@vadai.me>


[ Upstream commit 95c2027bfeda21a28eb245121e6a249f38d0788e ]

Add a validation function to make sure offset is valid:
1. Not below skb head (could happen when offset is negative).
2. Validate both 'offset' and 'at'.

Signed-off-by: Amir Vadai <amir@vadai.me>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/act_pedit.c |   24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -108,6 +108,17 @@ static void tcf_pedit_cleanup(struct tc_
 	kfree(keys);
 }
 
+static bool offset_valid(struct sk_buff *skb, int offset)
+{
+	if (offset > 0 && offset > skb->len)
+		return false;
+
+	if  (offset < 0 && -offset > skb_headroom(skb))
+		return false;
+
+	return true;
+}
+
 static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
 		     struct tcf_result *res)
 {
@@ -134,6 +145,11 @@ static int tcf_pedit(struct sk_buff *skb
 			if (tkey->offmask) {
 				char *d, _d;
 
+				if (!offset_valid(skb, off + tkey->at)) {
+					pr_info("tc filter pedit 'at' offset %d out of bounds\n",
+						off + tkey->at);
+					goto bad;
+				}
 				d = skb_header_pointer(skb, off + tkey->at, 1,
 						       &_d);
 				if (!d)
@@ -146,10 +162,10 @@ static int tcf_pedit(struct sk_buff *skb
 					" offset must be on 32 bit boundaries\n");
 				goto bad;
 			}
-			if (offset > 0 && offset > skb->len) {
-				pr_info("tc filter pedit"
-					" offset %d can't exceed pkt length %d\n",
-				       offset, skb->len);
+
+			if (!offset_valid(skb, off + offset)) {
+				pr_info("tc filter pedit offset %d out of bounds\n",
+					offset);
 				goto bad;
 			}
 


Patches currently in stable-queue which might be from amir@vadai.me are

queue-4.8/net-sched-pedit-make-sure-that-offset-is-valid.patch