[Devel] [PATCH RHEL7 COMMIT] netfilter: nf_tables: fib: use skb_header_pointer

[Vasily Averin]

The commit is pushed to "branch-rh7-3.10.0-1160.11.1.vz7.172.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.11.1.vz7.172.12
------>
commit fff709909068f009df1e047751f9a41c0e1dcda0
Author: Pablo M. Bermudo Garay <pablombg at gmail.com>
Date:   Fri Feb 5 14:32:25 2021 +0300

    netfilter: nf_tables: fib: use skb_header_pointer
    
    This is a preparatory patch for adding fib support to the netdev family.
    
    The netdev family receives the packets from ingress hook. At this point
    we have no guarantee that the ip header is linear. So this patch
    replaces ip_hdr with skb_header_pointer in order to address that
    possible situation.
    
    Signed-off-by: Pablo M. Bermudo Garay <pablombg at gmail.com>
    Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
    
    https://jira.sw.ru/browse/PSBM-125002
    (cherry picked from commit f347ec852c7a83e1803192d2c1fce4e42e0715a5)
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 net/ipv4/netfilter/nft_fib_ipv4.c | 20 ++++++++++++++++----
 net/ipv6/netfilter/nft_fib_ipv6.c | 29 +++++++++++++++++++++++------
 2 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c
index 624f8b9..8c21517 100644
--- a/net/ipv4/netfilter/nft_fib_ipv4.c
+++ b/net/ipv4/netfilter/nft_fib_ipv4.c
@@ -32,9 +32,10 @@ void nft_fib4_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
 			const struct nft_pktinfo *pkt)
 {
 	const struct nft_fib *priv = nft_expr_priv(expr);
+	int noff = skb_network_offset(pkt->skb);
 	u32 *dst = &regs->data[priv->dreg];
 	const struct net_device *dev = NULL;
-	const struct iphdr *iph;
+	struct iphdr *iph, _iph;
 	__be32 addr;
 
 	if (priv->flags & NFTA_FIB_F_IIF)
@@ -42,7 +43,12 @@ void nft_fib4_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
 	else if (priv->flags & NFTA_FIB_F_OIF)
 		dev = nft_out(pkt);
 
-	iph = ip_hdr(pkt->skb);
+	iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
+	if (!iph) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
 	if (priv->flags & NFTA_FIB_F_DADDR)
 		addr = iph->daddr;
 	else
@@ -61,8 +67,9 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
 		   const struct nft_pktinfo *pkt)
 {
 	const struct nft_fib *priv = nft_expr_priv(expr);
+	int noff = skb_network_offset(pkt->skb);
 	u32 *dest = &regs->data[priv->dreg];
-	const struct iphdr *iph;
+	struct iphdr *iph, _iph;
 	struct fib_result res;
 	struct flowi4 fl4 = {
 		.flowi4_scope = RT_SCOPE_UNIVERSE,
@@ -95,7 +102,12 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
 		return;
 	}
 
-	iph = ip_hdr(pkt->skb);
+	iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
+	if (!iph) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
 	if (ipv4_is_zeronet(iph->saddr)) {
 		if (ipv4_is_lbcast(iph->daddr) ||
 		    ipv4_is_local_multicast(iph->daddr)) {
diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index e8d88d8..15af254 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -25,9 +25,9 @@ static int get_ifindex(const struct net_device *dev)
 
 static int nft_fib6_flowi_init(struct flowi6 *fl6, const struct nft_fib *priv,
 			       const struct nft_pktinfo *pkt,
-			       const struct net_device *dev)
+			       const struct net_device *dev,
+			       struct ipv6hdr *iph)
 {
-	const struct ipv6hdr *iph = ipv6_hdr(pkt->skb);
 	int lookup_flags = 0;
 
 	if (priv->flags & NFTA_FIB_F_DADDR) {
@@ -55,7 +55,8 @@ static int nft_fib6_flowi_init(struct flowi6 *fl6, const struct nft_fib *priv,
 }
 
 static u32 __nft_fib6_eval_type(const struct nft_fib *priv,
-				const struct nft_pktinfo *pkt)
+				const struct nft_pktinfo *pkt,
+				struct ipv6hdr *iph)
 {
 	const struct net_device *dev = NULL;
 	const struct nf_ipv6_ops *v6ops;
@@ -77,7 +78,7 @@ static u32 __nft_fib6_eval_type(const struct nft_fib *priv,
 	else if (priv->flags & NFTA_FIB_F_OIF)
 		dev = nft_out(pkt);
 
-	nft_fib6_flowi_init(&fl6, priv, pkt, dev);
+	nft_fib6_flowi_init(&fl6, priv, pkt, dev, iph);
 
 	v6ops = nf_get_ipv6_ops();
 	if (dev && v6ops && v6ops->chk_addr(nft_net(pkt), &fl6.daddr, dev, true))
@@ -131,9 +132,17 @@ void nft_fib6_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
 			const struct nft_pktinfo *pkt)
 {
 	const struct nft_fib *priv = nft_expr_priv(expr);
+	int noff = skb_network_offset(pkt->skb);
 	u32 *dest = &regs->data[priv->dreg];
+	struct ipv6hdr *iph, _iph;
 
-	*dest = __nft_fib6_eval_type(priv, pkt);
+	iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
+	if (!iph) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	*dest = __nft_fib6_eval_type(priv, pkt, iph);
 }
 EXPORT_SYMBOL_GPL(nft_fib6_eval_type);
 
@@ -141,8 +150,10 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
 		   const struct nft_pktinfo *pkt)
 {
 	const struct nft_fib *priv = nft_expr_priv(expr);
+	int noff = skb_network_offset(pkt->skb);
 	const struct net_device *oif = NULL;
 	u32 *dest = &regs->data[priv->dreg];
+	struct ipv6hdr *iph, _iph;
 	struct flowi6 fl6 = {
 		.flowi6_iif = LOOPBACK_IFINDEX,
 		.flowi6_proto = pkt->tprot,
@@ -155,7 +166,13 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
 	else if (priv->flags & NFTA_FIB_F_OIF)
 		oif = nft_out(pkt);
 
-	lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif);
+	iph = skb_header_pointer(pkt->skb, noff, sizeof(_iph), &_iph);
+	if (!iph) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif, iph);
 
 	if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
 	    nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {