[PATCH Trusty] ipv6: Check ip6_find_1stfragopt() return value properly.

[Po-Hsu Lin]

From: "David S. Miller" <davem at davemloft.net>

Do not use unsigned variables to see if it returns a negative
error or not.

Fixes: 2423496af35d ("ipv6: Prevent overrun when parsing v6 header options")
Reported-by: Julia Lawall <julia.lawall at lip6.fr>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit 7dd7eb9513bd02184d45f000ab69d78cb1fa1531)

Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 net/ipv6/ip6_offload.c |   10 +++++-----
 net/ipv6/ip6_output.c  |    7 +++----
 net/ipv6/udp_offload.c |    8 +++++---
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 62dcb60..89b79cc 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -86,7 +86,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	const struct net_offload *ops;
 	int proto;
 	struct frag_hdr *fptr;
-	unsigned int unfrag_ip6hlen;
+	unsigned int payload_len;
 	u8 *prevhdr;
 	int offset = 0;
 	bool encap, udpfrag;
@@ -142,10 +142,10 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 		skb->network_header = (u8 *)ipv6h - skb->head;
 
 		if (udpfrag) {
-			unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
-			if (unfrag_ip6hlen < 0)
-				return ERR_PTR(unfrag_ip6hlen);
-			fptr = (struct frag_hdr *)((u8 *)ipv6h + unfrag_ip6hlen);
+			int err = ip6_find_1stfragopt(skb, &prevhdr);
+			if (err < 0)
+				return ERR_PTR(err);
+			fptr = (struct frag_hdr *)((u8 *)ipv6h + err);
 			fptr->frag_off = htons(offset);
 			if (skb->next != NULL)
 				fptr->frag_off |= htons(IP6_MF);
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 9efa30a..e3d4f5d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -545,11 +545,10 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	u8 *prevhdr, nexthdr = 0;
 	struct net *net = dev_net(skb_dst(skb)->dev);
 
-	hlen = ip6_find_1stfragopt(skb, &prevhdr);
-	if (hlen < 0) {
-		err = hlen;
+	err = ip6_find_1stfragopt(skb, &prevhdr);
+	if (err < 0)
 		goto fail;
-	}
+	hlen = err;
 	nexthdr = *prevhdr;
 
 	mtu = ip6_skb_dst_mtu(skb);
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index f315f43..d806113 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -51,6 +51,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 	int offset;
 	__wsum csum;
 	int tnl_hlen;
+	int err;
 
 	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
@@ -98,9 +99,10 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		/* Find the unfragmentable header and shift it left by frag_hdr_sz
 		 * bytes to insert fragment header.
 		 */
-		unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
-		if (unfrag_ip6hlen < 0)
-			return ERR_PTR(unfrag_ip6hlen);
+		err = ip6_find_1stfragopt(skb, &prevhdr);
+		if (err < 0)
+			return ERR_PTR(err);
+		unfrag_ip6hlen = err;
 		nexthdr = *prevhdr;
 		*prevhdr = NEXTHDR_FRAGMENT;
 		unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
-- 
1.7.9.5