CVE-2013-4470 (published 2013-11-04T15:55Z)

The Linux kernel before 3.12, when UDP Fragmentation Offload (UFO) is enabled, does not properly initialize certain data structures, which allows local users to cause a denial of service (memory corruption and system crash) or possibly gain privileges via a crafted application that uses the UDP_CORK option in a setsockopt system call and sends both short and long packets, related to the ip_ufo_append_data function in net/ipv4/ip_output.c and the ip6_ufo_append_data function in net/ipv6/ip6_output.c.

Severity: MEDIUM
CVSS v2 base score: 6.9 (AV:L/AC:M/Au:N/C:C/I:C/A:C)

Weakness information:
cwe_id: CWE-264
cwe_name: Permissions, Privileges, and Access Controls
description: Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Jiri Pirko
author_date: 2013-10-19 12:29:16+02:00
msg: ip6_output: do skb ufo init for peeked non ufo skb as well

Now, if user application does:
sendto len<mtu flag MSG_MORE
sendto len>mtu flag 0
The skb is not treated as fragmented one because it is not initialized
that way. So move the initialization to fix this.

introduced by:
commit e89e9cf539a28df7d0eb1d0a545368e9920b34ac "[IPv4/IPv6]: UFO Scatter-gather approach"

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: ip6_output.c
change_type: ModificationType.MODIFY
diff: @@ -1008,6 +1008,7 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 
 {
 	struct sk_buff *skb;
+	struct frag_hdr fhdr;
 	int err;
 
 	/* There is support for UDP large send offload by network
@@ -1015,8 +1016,6 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 	 * udp datagram
 	 */
 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
-		struct frag_hdr fhdr;
-
 		skb = sock_alloc_send_skb(sk,
 			hh_len + fragheaderlen + transhdrlen + 20,
 			(flags & MSG_DONTWAIT), &err);
@@ -1036,20 +1035,24 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 		skb->transport_header = skb->network_header + fragheaderlen;
 
 		skb->protocol = htons(ETH_P_IPV6);
-		skb->ip_summed = CHECKSUM_PARTIAL;
 		skb->csum = 0;
 
-		/* Specify the length of each IPv6 datagram fragment.
-		 * It has to be a multiple of 8.
-		 */
-		skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
-					     sizeof(struct frag_hdr)) & ~7;
-		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
-		ipv6_select_ident(&fhdr, rt);
-		skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
 		__skb_queue_tail(&sk->sk_write_queue, skb);
+	} else if (skb_is_gso(skb)) {
+		goto append;
 	}
 
+	skb->ip_summed = CHECKSUM_PARTIAL;
+	/* Specify the length of each IPv6 datagram fragment.
+	 * It has to be a multiple of 8.
+	 */
+	skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
+				     sizeof(struct frag_hdr)) & ~7;
+	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+	ipv6_select_ident(&fhdr, rt);
+	skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
+
+append:
 	return skb_append_datato_frags(sk, skb, getfrag, from,
 				       (length - transhdrlen));
 }

programming_language: C
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Jiri Pirko
author_date: 2013-10-19 12:29:17+02:00
msg: ip_output: do skb ufo init for peeked non ufo skb as well

Now, if user application does:
sendto len<mtu flag MSG_MORE
sendto len>mtu flag 0
The skb is not treated as fragmented one because it is not initialized
that way. So move the initialization to fix this.

introduced by:
commit e89e9cf539a28df7d0eb1d0a545368e9920b34ac "[IPv4/IPv6]: UFO Scatter-gather approach"

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: ip_output.c
change_type: ModificationType.MODIFY
diff: @@ -772,15 +772,20 @@ static inline int ip_ufo_append_data(struct sock *sk,
 		/* initialize protocol header pointer */
 		skb->transport_header = skb->network_header + fragheaderlen;
 
-		skb->ip_summed = CHECKSUM_PARTIAL;
 		skb->csum = 0;
 
-		/* specify the length of each IP datagram fragment */
-		skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
-		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+
 		__skb_queue_tail(queue, skb);
+	} else if (skb_is_gso(skb)) {
+		goto append;
 	}
 
+	skb->ip_summed = CHECKSUM_PARTIAL;
+	/* specify the length of each IP datagram fragment */
+	skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
+	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+
+append:
 	return skb_append_datato_frags(sk, skb, getfrag, from,
 				       (length - transhdrlen));
 }

programming_language: C