netdev - [PATCH ipsec] esp4: add length check for UDP encapsulation

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <2271cf907a9b608387a6a19dbbfdb45c99626b15.1553520487.git.sd@queasysnail.net>
Date:   Mon, 25 Mar 2019 14:30:00 +0100
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Sabrina Dubroca <sd@...asysnail.net>
Subject: [PATCH ipsec] esp4: add length check for UDP encapsulation

esp_output_udp_encap can produce a length that doesn't fit in the 16
bits of a UDP header's length field. In that case, we'll send a
fragmented packet whose length is larger than IP_MAX_MTU (resulting in
"Oversized IP packet" warnings on receive) and with a bogus UDP
length.

To prevent this, add a length check to esp_output_udp_encap and return
 -EMSGSIZE on failure.

This seems to be older than git history.

Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/ipv4/esp4.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 10e809b296ec..fb065a8937ea 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -226,7 +226,7 @@ static void esp_output_fill_trailer(u8 *tail, int tfclen, int plen, __u8 proto)
 	tail[plen - 1] = proto;
 }
 
-static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
+static int esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
 {
 	int encap_type;
 	struct udphdr *uh;
@@ -234,6 +234,7 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
 	__be16 sport, dport;
 	struct xfrm_encap_tmpl *encap = x->encap;
 	struct ip_esp_hdr *esph = esp->esph;
+	unsigned int len;
 
 	spin_lock_bh(&x->lock);
 	sport = encap->encap_sport;
@@ -241,11 +242,14 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
 	encap_type = encap->encap_type;
 	spin_unlock_bh(&x->lock);
 
+	len = skb->len + esp->tailen - skb_transport_offset(skb);
+	if (len + sizeof(struct iphdr) >= IP_MAX_MTU)
+		return -EMSGSIZE;
+
 	uh = (struct udphdr *)esph;
 	uh->source = sport;
 	uh->dest = dport;
-	uh->len = htons(skb->len + esp->tailen
-		  - skb_transport_offset(skb));
+	uh->len = htons(len);
 	uh->check = 0;
 
 	switch (encap_type) {
@@ -262,6 +266,8 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
 
 	*skb_mac_header(skb) = IPPROTO_UDP;
 	esp->esph = esph;
+
+	return 0;
 }
 
 int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
@@ -275,8 +281,12 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
 	int tailen = esp->tailen;
 
 	/* this is non-NULL only with UDP Encapsulation */
-	if (x->encap)
-		esp_output_udp_encap(x, skb, esp);
+	if (x->encap) {
+		int err = esp_output_udp_encap(x, skb, esp);
+
+		if (err < 0)
+			return err;
+	}
 
 	if (!skb_cloned(skb)) {
 		if (tailen <= skb_tailroom(skb)) {
-- 
2.21.0