Fix pnstrdup() to not memcpy() the maximum allowed length.

The previous behaviour was dangerous if the length passed wasn't the
size of the underlying buffer, but the maximum size of the underlying
buffer.

Author: Andres Freund
Discussion: https://postgr.es/m/20161003215524.mwz5p45pcverrkyk@alap3.anarazel.de

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index cd696f16bc764238b8706f67bc7486a5c2c1d98e..64e0408d5afc9d19d8ee2e6a9b0e6d5743a8fc35 100644 (file)
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -21,6 +21,7 @@
 
 #include "postgres.h"
 
+#include "common/string.h"
 #include "miscadmin.h"
 #include "utils/memdebug.h"
 #include "utils/memutils.h"
@@ -1086,10 +1087,14 @@ pstrdup(const char *in)
 char *
 pnstrdup(const char *in, Size len)
 {
-       char       *out = palloc(len + 1);
+       char       *out;
 
+       len = pg_strnlen(in, len);
+
+       out = palloc(len + 1);
        memcpy(out, in, len);
        out[len] = '\0';
+
        return out;
 }