[PATCH nft] evaluate: fix memleak in prefix evaluation with wildcard interface name

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

The following ruleset:

  table ip x {
        chain y {
                meta iifname { abcde*, xyz }
        }
  }

triggers the following memleak:

==6871== 16 bytes in 1 blocks are definitely lost in loss record 1 of 1
==6871==    at 0x483877F: malloc (vg_replace_malloc.c:307)
==6871==    by 0x48AD898: xmalloc (utils.c:37)
==6871==    by 0x4BC8B22: __gmpz_init2 (in /usr/lib/x86_64-linux-gnu/libgmp.so.10.4.1)
==6871==    by 0x4887E67: constant_expr_alloc (expression.c:424)
==6871==    by 0x488EF1F: expr_evaluate_prefix (evaluate.c:1138)
==6871==    by 0x488EF1F: expr_evaluate (evaluate.c:2725)
==6871==    by 0x488E76D: expr_evaluate_set_elem (evaluate.c:1662)
==6871==    by 0x488E76D: expr_evaluate (evaluate.c:2739)
==6871==    by 0x4891033: list_member_evaluate (evaluate.c:1454)
==6871==    by 0x488E2B6: expr_evaluate_set (evaluate.c:1757)
==6871==    by 0x488E2B6: expr_evaluate (evaluate.c:2737)
==6871==    by 0x48910D0: elems_evaluate (evaluate.c:4605)
==6871==    by 0x4891432: set_evaluate (evaluate.c:4711)
==6871==    by 0x48915BC: implicit_set_declaration (evaluate.c:122)
==6871==    by 0x488F18A: expr_evaluate_relational (evaluate.c:2503)
==6871==    by 0x488F18A: expr_evaluate (evaluate.c:2745)

expr_evaluate_prefix() calls constant_expr_alloc() which have already
called mpz_init2(), the second call to mpz_init2() overlaps the existing
mpz_t data memory area.

Remove extra mpz_init2() call to fix this memleak.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/evaluate.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/evaluate.c b/src/evaluate.c
index 1b7e0b37b61b..90e7bff62cce 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1142,7 +1142,6 @@ static int expr_evaluate_prefix(struct eval_ctx *ctx, struct expr **expr)
 		mpz_prefixmask(mask->value, base->len, prefix->prefix_len);
 		break;
 	case TYPE_STRING:
-		mpz_init2(mask->value, base->len);
 		mpz_bitmask(mask->value, prefix->prefix_len);
 		break;
 	}
-- 
2.30.2