[SRU,Trusty,Zesty,1/1] ipv6: avoid overflow of offset in ip6_find_1stfragopt

Message ID 20171130131349.12302-2-kleber.souza@canonical.com
State New
Headers show
Series
  • Fix for CVE-2017-7542
Related show

Commit Message

Kleber Souza Nov. 30, 2017, 1:13 p.m.
From: Sabrina Dubroca <sd@queasysnail.net>

In some cases, offset can overflow and can cause an infinite loop in
ip6_find_1stfragopt(). Make it unsigned int to prevent the overflow, and
cap it at IPV6_MAXPLEN, since packets larger than that should be invalid.

This problem has been here since before the beginning of git history.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

CVE-2017-7542
(cherry picked from commit 6399f1fae4ec29fab5ec76070435555e256ca3a6)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
---
 net/ipv6/output_core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Colin King Nov. 30, 2017, 1:42 p.m. | #1
On 30/11/17 13:13, Kleber Sacilotto de Souza wrote:
> From: Sabrina Dubroca <sd@queasysnail.net>
> 
> In some cases, offset can overflow and can cause an infinite loop in
> ip6_find_1stfragopt(). Make it unsigned int to prevent the overflow, and
> cap it at IPV6_MAXPLEN, since packets larger than that should be invalid.
> 
> This problem has been here since before the beginning of git history.
> 
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> CVE-2017-7542
> (cherry picked from commit 6399f1fae4ec29fab5ec76070435555e256ca3a6)
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
> ---
>  net/ipv6/output_core.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
> index e9065b8d3af8..abb2c307fbe8 100644
> --- a/net/ipv6/output_core.c
> +++ b/net/ipv6/output_core.c
> @@ -78,7 +78,7 @@ EXPORT_SYMBOL(ipv6_select_ident);
>  
>  int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
>  {
> -	u16 offset = sizeof(struct ipv6hdr);
> +	unsigned int offset = sizeof(struct ipv6hdr);
>  	unsigned int packet_len = skb_tail_pointer(skb) -
>  		skb_network_header(skb);
>  	int found_rhdr = 0;
> @@ -86,6 +86,7 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
>  
>  	while (offset <= packet_len) {
>  		struct ipv6_opt_hdr *exthdr;
> +		unsigned int len;
>  
>  		switch (**nexthdr) {
>  
> @@ -111,7 +112,10 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
>  
>  		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
>  						 offset);
> -		offset += ipv6_optlen(exthdr);
> +		len = ipv6_optlen(exthdr);
> +		if (len + offset >= IPV6_MAXPLEN)
> +			return -EINVAL;
> +		offset += len;
>  		*nexthdr = &exthdr->nexthdr;
>  	}
>  
> 
Clean upstream cherry pick, looks totally fine to me.

Acked-by: Colin Ian King <colin.king@canonical.com>

Patch

diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
index e9065b8d3af8..abb2c307fbe8 100644
--- a/net/ipv6/output_core.c
+++ b/net/ipv6/output_core.c
@@ -78,7 +78,7 @@  EXPORT_SYMBOL(ipv6_select_ident);
 
 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 {
-	u16 offset = sizeof(struct ipv6hdr);
+	unsigned int offset = sizeof(struct ipv6hdr);
 	unsigned int packet_len = skb_tail_pointer(skb) -
 		skb_network_header(skb);
 	int found_rhdr = 0;
@@ -86,6 +86,7 @@  int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 
 	while (offset <= packet_len) {
 		struct ipv6_opt_hdr *exthdr;
+		unsigned int len;
 
 		switch (**nexthdr) {
 
@@ -111,7 +112,10 @@  int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 
 		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
 						 offset);
-		offset += ipv6_optlen(exthdr);
+		len = ipv6_optlen(exthdr);
+		if (len + offset >= IPV6_MAXPLEN)
+			return -EINVAL;
+		offset += len;
 		*nexthdr = &exthdr->nexthdr;
 	}