Patch "ip6_gre: fix ip6gre_err() invalid reads" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ip6_gre: fix ip6gre_err() invalid reads

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ip6_gre-fix-ip6gre_err-invalid-reads.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Sat, 4 Feb 2017 23:18:55 -0800
Subject: ip6_gre: fix ip6gre_err() invalid reads

From: Eric Dumazet <[email protected]>

[ Upstream commit 7892032cfe67f4bde6fc2ee967e45a8fbaf33756 ]

Andrey Konovalov reported out of bound accesses in ip6gre_err()

If GRE flags contains GRE_KEY, the following expression *(((__be32 *)p) + (grehlen / 4) - 1)

accesses data ~40 bytes after the expected point, since grehlen includes the size of IPv6 headers.

Let's use a "struct gre_base_hdr *greh" pointer to make this code more readable.

p[1] becomes greh->protocol.
grhlen is the GRE header length.

---
 net/ipv6/ip6_gre.c |   41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

@@ -55,6 +55,7 @@
 #include <net/ip6_fib.h>
 #include <net/ip6_route.h>
 #include <net/ip6_tunnel.h>
+#include <net/gre.h>
 
 
 static bool log_ecn_error = true;

@@ -367,35 +368,37 @@ static void ip6gre_tunnel_uninit(struct
 
 
 static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
-		u8 type, u8 code, int offset, __be32 info)
+		       u8 type, u8 code, int offset, __be32 info)
 {
-	const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)skb->data;
-	__be16 *p = (__be16 *)(skb->data + offset);
-	int grehlen = offset + 4;
+	const struct gre_base_hdr *greh;
+	const struct ipv6hdr *ipv6h;
+	int grehlen = sizeof(*greh);
 	struct ip6_tnl *t;
+	int key_off = 0;
 	__be16 flags;
+	__be32 key;
 
-	flags = p[0];
-	if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
-		if (flags&(GRE_VERSION|GRE_ROUTING))
-			return;
-		if (flags&GRE_KEY) {
-			grehlen += 4;
-			if (flags&GRE_CSUM)
-				grehlen += 4;
-		}
+	if (!pskb_may_pull(skb, offset + grehlen))
+		return;
+	greh = (const struct gre_base_hdr *)(skb->data + offset);
+	flags = greh->flags;
+	if (flags & (GRE_VERSION | GRE_ROUTING))
+		return;
+	if (flags & GRE_CSUM)
+		grehlen += 4;
+	if (flags & GRE_KEY) {
+		key_off = grehlen + offset;
+		grehlen += 4;
 	}
 
-	/* If only 8 bytes returned, keyed message will be dropped here */
-	if (!pskb_may_pull(skb, grehlen))
+	if (!pskb_may_pull(skb, offset + grehlen))
 		return;
 	ipv6h = (const struct ipv6hdr *)skb->data;
-	p = (__be16 *)(skb->data + offset);
+	greh = (const struct gre_base_hdr *)(skb->data + offset);
+	key = key_off ? *(__be32 *)(skb->data + key_off) : 0;
 
 	t = ip6gre_tunnel_lookup(skb->dev, &ipv6h->daddr, &ipv6h->saddr,
-				flags & GRE_KEY ?
-				*(((__be32 *)p) + (grehlen / 4) - 1) : 0,
-				p[1]);
+				 key, greh->protocol);
 	if (!t)
 		return;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ipv6-pointer-math-error-in-ip6_tnl_parse_tlv_enc_lim.patch queue-4.4/netlabel-out-of-bound-access-in-cipso_v4_validate.patch queue-4.4/packet-round-up-linear-to-header-len.patch queue-4.4/tun-read-vnet_hdr_sz-once.patch queue-4.4/ipv6-fix-ip6_tnl_parse_tlv_enc_lim.patch queue-4.4/l2tp-do-not-use-udp_ioctl.patch queue-4.4/tcp-fix-0-divide-in-__tcp_select_window.patch queue-4.4/can-fix-kernel-panic-at-security_sock_rcv_skb.patch queue-4.4/net-introduce-device-min_header_len.patch queue-4.4/macvtap-read-vnet_hdr_size-once.patch queue-4.4/tcp-avoid-infinite-loop-in-tcp_splice_read.patch queue-4.4/mlx4-invoke-softirqs-after-napi_reschedule.patch queue-4.4/ipv6-tcp-add-a-missing-tcp_v6_restore_cb.patch queue-4.4/ipv4-keep-skb-dst-around-in-presence-of-ip-options.patch queue-4.4/net-use-a-work-queue-to-defer-net_disable_timestamp-work.patch queue-4.4/ip6_gre-fix-ip6gre_err-invalid-reads.patch