[PATCH nft 1/7] segtree: perform stricter expression type validation from expr_value()

[Pablo Neira Ayuso <pablo@netfilter.org>]

This helper function returns a expression value type that represents the
set element key. This functions currently expects two kind of
expressions: set elements and mappings.

Bail out otherwise, if we see anything else, we have to fix our code.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/segtree.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/segtree.c b/src/segtree.c
index 060951c..5b69ffb 100644
--- a/src/segtree.c
+++ b/src/segtree.c
@@ -473,10 +473,14 @@ extern void interval_map_decompose(struct expr *set);
 
 static struct expr *expr_value(struct expr *expr)
 {
-	if (expr->ops->type == EXPR_MAPPING)
+	switch (expr->ops->type) {
+	case EXPR_MAPPING:
 		return expr->left->key;
-	else
+	case EXPR_SET_ELEM:
 		return expr->key;
+	default:
+		BUG("invalid expression type %s\n", expr->ops->name);
+	}
 }
 
 static int expr_value_cmp(const void *p1, const void *p2)
-- 
2.1.4