netdev - [PATCH] act_pedit: access skb->data safely

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-next>] [day] [month] [year] [list]

Date:	Wed,  2 Jun 2010 22:55:02 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Jamal Hadi Salim <hadi@...erus.ca>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Changli Gao <xiaosuo@...il.com>
Subject: [PATCH] act_pedit: access skb->data safely

access skb->data safely

we should use skb_header_pointer() and skb_store_bits() to access skb->data to
handle small or non-linear skbs.

Signed-off-by: Changli Gao <xiaosuo@...il.com>
----
 net/sched/act_pedit.c |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index fdbd0b7..50e3d94 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -125,7 +125,7 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
 {
 	struct tcf_pedit *p = a->priv;
 	int i, munged = 0;
-	u8 *pptr;
+	unsigned int off;
 
 	if (!(skb->tc_verd & TC_OK2MUNGE)) {
 		/* should we set skb->cloned? */
@@ -134,7 +134,7 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
 		}
 	}
 
-	pptr = skb_network_header(skb);
+	off = skb_network_offset(skb);
 
 	spin_lock(&p->tcf_lock);
 
@@ -144,17 +144,17 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
 		struct tc_pedit_key *tkey = p->tcfp_keys;
 
 		for (i = p->tcfp_nkeys; i > 0; i--, tkey++) {
-			u32 *ptr;
+			u32 *ptr, _data;
 			int offset = tkey->off;
 
 			if (tkey->offmask) {
-				if (skb->len > tkey->at) {
-					 char *j = pptr + tkey->at;
-					 offset += ((*j & tkey->offmask) >>
-						   tkey->shift);
-				} else {
+				char *d, _d;
+
+				d = skb_header_pointer(skb, off + tkey->at, 1,
+						       &_d);
+				if (!d)
 					goto bad;
-				}
+				offset += (*d & tkey->offmask) >> tkey->shift;
 			}
 
 			if (offset % 4) {
@@ -169,9 +169,13 @@ static int tcf_pedit(struct sk_buff *skb, struct tc_action *a,
 				goto bad;
 			}
 
-			ptr = (u32 *)(pptr+offset);
+			ptr = skb_header_pointer(skb, off + offset, 4, &_data);
+			if (!ptr)
+				goto bad;
 			/* just do it, baby */
 			*ptr = ((*ptr & tkey->mask) ^ tkey->val);
+			if (ptr == &_data)
+				skb_store_bits(skb, off + offset, ptr, 4);
 			munged++;
 		}
 
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html