[PATCH nft] netlink_delinearize: fix use-after-free

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We have to clone the payload expression before attaching it to the lhs
of the relational expression, this payload expression is located at the
lhs of the binary operation that is released thereafter.

Fixes: 39f15c2 ("nft: support listing expressions that use non-byte header fields")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
 src/netlink_delinearize.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index b119027..1ab8f43 100644
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -1217,8 +1217,8 @@ static void relational_binop_postprocess(struct rule_pp_ctx *ctx, struct expr *e
 	} else if (binop->op == OP_AND &&
 		   binop->left->ops->type == EXPR_PAYLOAD &&
 		   binop->right->ops->type == EXPR_VALUE) {
-		struct expr *payload = expr->left->left;
-		struct expr *mask = expr->left->right;
+		struct expr *payload = binop->left;
+		struct expr *mask = binop->right;
 
 		/*
 		 * This *might* be a payload match testing header fields that
@@ -1266,7 +1266,7 @@ static void relational_binop_postprocess(struct rule_pp_ctx *ctx, struct expr *e
 			assert(expr->left->ops->type == EXPR_BINOP);
 
 			assert(binop->left == payload);
-			expr->left = payload;
+			expr->left = expr_clone(payload);
 			expr_free(binop);
 		}
 	}
-- 
2.1.4

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