hesiod: Avoid heap overflow in get_txt_records [BZ #20031]

(cherry picked from commit 8a03ccbb77f52ec4b55062eeedddb8daec1a33e4)
(cherry picked from commit 4c4b3cbb4638ec19de19c167d498e30fd67501ab)

diff --git a/hesiod/hesiod.c b/hesiod/hesiod.c
index 5b13b3f1c443a566f62cebcc09bde4472dc87a92..98ddee39a401b2bbcd9533e2209b179b7afec9a4 100644 (file)
--- a/hesiod/hesiod.c
+++ b/hesiod/hesiod.c
@@ -411,7 +411,7 @@ get_txt_records(struct hesiod_p *ctx, int class, const char *name) {
                cp += INT16SZ + INT32SZ;        /* skip the ttl, too */
                rr.dlen = ns_get16(cp);
                cp += INT16SZ;
-               if (cp + rr.dlen > eom) {
+               if (rr.dlen == 0 || cp + rr.dlen > eom) {
                        __set_errno(EMSGSIZE);
                        goto cleanup;
                }