linux-kernel - [PATCH 3.16 062/157] xfrm4: Reload skb header pointers after calling pskb_may

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Message-ID: <lsq.1565469607.86940932@decadent.org.uk>
Date:   Sat, 10 Aug 2019 21:40:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Steffen Klassert" <steffen.klassert@...unet.com>
Subject: [PATCH 3.16 062/157] xfrm4: Reload skb header pointers after
 calling pskb_may_pull.

3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steffen Klassert <steffen.klassert@...unet.com>

commit ea673a4d3a337184f3c314dcc6300bf02f39e077 upstream.

A call to pskb_may_pull may change the pointers into the packet,
so reload the pointers after the call.

Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv4/xfrm4_policy.c | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -123,7 +123,10 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_DCCP:
 			if (xprth + 4 < skb->data ||
 			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
-				__be16 *ports = (__be16 *)xprth;
+				__be16 *ports;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				ports = (__be16 *)xprth;
 
 				fl4->fl4_sport = ports[!!reverse];
 				fl4->fl4_dport = ports[!reverse];
@@ -133,7 +136,10 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_ICMP:
 			if (xprth + 2 < skb->data ||
 			    pskb_may_pull(skb, xprth + 2 - skb->data)) {
-				u8 *icmp = xprth;
+				u8 *icmp;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				icmp = xprth;
 
 				fl4->fl4_icmp_type = icmp[0];
 				fl4->fl4_icmp_code = icmp[1];
@@ -143,7 +149,10 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_ESP:
 			if (xprth + 4 < skb->data ||
 			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
-				__be32 *ehdr = (__be32 *)xprth;
+				__be32 *ehdr;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				ehdr = (__be32 *)xprth;
 
 				fl4->fl4_ipsec_spi = ehdr[0];
 			}
@@ -152,7 +161,10 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_AH:
 			if (xprth + 8 < skb->data ||
 			    pskb_may_pull(skb, xprth + 8 - skb->data)) {
-				__be32 *ah_hdr = (__be32 *)xprth;
+				__be32 *ah_hdr;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				ah_hdr = (__be32 *)xprth;
 
 				fl4->fl4_ipsec_spi = ah_hdr[1];
 			}
@@ -161,7 +173,10 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_COMP:
 			if (xprth + 4 < skb->data ||
 			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
-				__be16 *ipcomp_hdr = (__be16 *)xprth;
+				__be16 *ipcomp_hdr;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				ipcomp_hdr = (__be16 *)xprth;
 
 				fl4->fl4_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
 			}
@@ -170,8 +185,12 @@ _decode_session4(struct sk_buff *skb, st
 		case IPPROTO_GRE:
 			if (xprth + 12 < skb->data ||
 			    pskb_may_pull(skb, xprth + 12 - skb->data)) {
-				__be16 *greflags = (__be16 *)xprth;
-				__be32 *gre_hdr = (__be32 *)xprth;
+				__be16 *greflags;
+				__be32 *gre_hdr;
+
+				xprth = skb_network_header(skb) + iph->ihl * 4;
+				greflags = (__be16 *)xprth;
+				gre_hdr = (__be32 *)xprth;
 
 				if (greflags[0] & GRE_KEY) {
 					if (greflags[0] & GRE_CSUM)