[PATCH nf-next] netfilter: nf_tables: do not update stateful expressions if lookup is inverted

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

Initialize set lookup matching element to NULL. Otherwise, the
NFT_LOOKUP_F_INV flag reverses the matching logic and it leads to
deference an uninitialized pointer to the matching element. Make sure
element data area and stateful expression are accessed if there is a
matching set element.

This patch undoes 24791b9aa1ab ("netfilter: nft_set_bitmap: initialize set
element extension in lookups") which is not required anymore.

Fixes: 339706bc21c1 ("netfilter: nft_lookup: update element stateful expression")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
 include/net/netfilter/nf_tables.h |  2 +-
 net/netfilter/nft_lookup.c        | 12 +++++++-----
 net/netfilter/nft_set_bitmap.c    |  1 -
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 6eb627b3c99b..4ff7c81e6717 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -901,7 +901,7 @@ static inline void nft_set_elem_update_expr(const struct nft_set_ext *ext,
 {
 	struct nft_expr *expr;
 
-	if (nft_set_ext_exists(ext, NFT_SET_EXT_EXPR)) {
+	if (__nft_set_ext_exists(ext, NFT_SET_EXT_EXPR)) {
 		expr = nft_set_ext_expr(ext);
 		expr->ops->eval(expr, regs, pkt);
 	}
diff --git a/net/netfilter/nft_lookup.c b/net/netfilter/nft_lookup.c
index 1e70359d633c..f1363b8aabba 100644
--- a/net/netfilter/nft_lookup.c
+++ b/net/netfilter/nft_lookup.c
@@ -29,7 +29,7 @@ void nft_lookup_eval(const struct nft_expr *expr,
 {
 	const struct nft_lookup *priv = nft_expr_priv(expr);
 	const struct nft_set *set = priv->set;
-	const struct nft_set_ext *ext;
+	const struct nft_set_ext *ext = NULL;
 	bool found;
 
 	found = set->ops->lookup(nft_net(pkt), set, &regs->data[priv->sreg],
@@ -39,11 +39,13 @@ void nft_lookup_eval(const struct nft_expr *expr,
 		return;
 	}
 
-	if (set->flags & NFT_SET_MAP)
-		nft_data_copy(&regs->data[priv->dreg],
-			      nft_set_ext_data(ext), set->dlen);
+	if (ext) {
+		if (set->flags & NFT_SET_MAP)
+			nft_data_copy(&regs->data[priv->dreg],
+				      nft_set_ext_data(ext), set->dlen);
 
-	nft_set_elem_update_expr(ext, regs, pkt);
+		nft_set_elem_update_expr(ext, regs, pkt);
+	}
 }
 
 static const struct nla_policy nft_lookup_policy[NFTA_LOOKUP_MAX + 1] = {
diff --git a/net/netfilter/nft_set_bitmap.c b/net/netfilter/nft_set_bitmap.c
index 32f0fc8be3a4..2a81ea421819 100644
--- a/net/netfilter/nft_set_bitmap.c
+++ b/net/netfilter/nft_set_bitmap.c
@@ -81,7 +81,6 @@ static bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
 	u32 idx, off;
 
 	nft_bitmap_location(set, key, &idx, &off);
-	*ext = NULL;
 
 	return nft_bitmap_active(priv->bitmap, idx, off, genmask);
 }
-- 
2.11.0