Only call memmove if the rdata length is non zero

This avoids undefined behaviour on zero length rdata where the
data pointer is NULL.

(cherry picked from commit 228cc557fe4ca29e34eccb3a1846d7f754879aed)

diff --git a/lib/dns/rdataslab.c b/lib/dns/rdataslab.c
index 24fdaa83a19425e4280565e5aa368f9a2d5e16c2..2b4cc4bed3f113429f0b49d6b7409d759bae0f22 100644 (file)
--- a/lib/dns/rdataslab.c
+++ b/lib/dns/rdataslab.c
@@ -320,7 +320,9 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
                                            ? DNS_RDATASLAB_OFFLINE
                                            : 0;
                }
-               memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+               if (x[i].rdata.length != 0) {
+                       memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+               }
                rawbuf += x[i].rdata.length;
        }