netfilter: nft_meta_bridge: add validate callback for get operations

Blamed commit added NFT_META_BRI_IIFHWADDR to the set validate callback,
yet this is a get operation.

Add a get validate callback and move the NFT_META_BRI_IIFHWADDR key
there.

AFAICS this is harmless, NFT_META_BRI_IIFHWADDR can deal with a NULL
input device and the set handler ignores a NFT_META_BRI_IIFHWADDR
operation, but it allows to read 4 bytes off bridge skb->cb[].

Fixes: cbd2257dc96e ("netfilter: nft_meta_bridge: introduce NFT_META_BRI_IIFHWADDR support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 23 insertions, 3 deletions

diff --git a/include/net/netfilter/nft_meta.h b/include/net/netfilter/nft_meta.h
index f74e63290603..6cf1d910bbf8 100644
--- a/include/net/netfilter/nft_meta.h
+++ b/include/net/netfilter/nft_meta.h
@@ -40,6 +40,8 @@ void nft_meta_set_eval(const struct nft_expr *expr,
 void nft_meta_set_destroy(const struct nft_ctx *ctx,
 			  const struct nft_expr *expr);
 
+int nft_meta_get_validate(const struct nft_ctx *ctx,
+			  const struct nft_expr *expr);
 int nft_meta_set_validate(const struct nft_ctx *ctx,
 			  const struct nft_expr *expr);
 
diff --git a/net/bridge/netfilter/nft_meta_bridge.c b/net/bridge/netfilter/nft_meta_bridge.c
index 219c40680260..3d95f68e0906 100644
--- a/net/bridge/netfilter/nft_meta_bridge.c
+++ b/net/bridge/netfilter/nft_meta_bridge.c
@@ -107,12 +107,30 @@ static int nft_meta_bridge_get_init(const struct nft_ctx *ctx,
 					NULL, NFT_DATA_VALUE, len);
 }
 
+static int nft_meta_bridge_get_validate(const struct nft_ctx *ctx,
+					const struct nft_expr *expr)
+{
+	struct nft_meta *priv = nft_expr_priv(expr);
+	unsigned int hooks;
+
+	switch (priv->key) {
+	case NFT_META_BRI_IIFHWADDR:
+		hooks = 1 << NF_BR_PRE_ROUTING;
+		break;
+	default:
+		return nft_meta_get_validate(ctx, expr);
+	}
+
+	return nft_chain_validate_hooks(ctx->chain, hooks);
+}
+
 static struct nft_expr_type nft_meta_bridge_type;
 static const struct nft_expr_ops nft_meta_bridge_get_ops = {
 	.type		= &nft_meta_bridge_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_meta)),
 	.eval		= nft_meta_bridge_get_eval,
 	.init		= nft_meta_bridge_get_init,
+	.validate	= nft_meta_bridge_get_validate,
 	.dump		= nft_meta_get_dump,
 };
 
@@ -168,7 +186,6 @@ static int nft_meta_bridge_set_validate(const struct nft_ctx *ctx,
 
 	switch (priv->key) {
 	case NFT_META_BRI_BROUTE:
-	case NFT_META_BRI_IIFHWADDR:
 		hooks = 1 << NF_BR_PRE_ROUTING;
 		break;
 	default:
diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index 9b5821c64442..0a43e0787a68 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -635,8 +635,8 @@ static int nft_meta_get_validate_xfrm(const struct nft_ctx *ctx)
 #endif
 }
 
-static int nft_meta_get_validate(const struct nft_ctx *ctx,
-				 const struct nft_expr *expr)
+int nft_meta_get_validate(const struct nft_ctx *ctx,
+			  const struct nft_expr *expr)
 {
 	const struct nft_meta *priv = nft_expr_priv(expr);
 
@@ -652,6 +652,7 @@ static int nft_meta_get_validate(const struct nft_ctx *ctx,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(nft_meta_get_validate);
 
 int nft_meta_set_validate(const struct nft_ctx *ctx,
 			  const struct nft_expr *expr)