memdup0: handle edge case

When length is already SIZE_MAX, fail without allocating.

Reported-by: Joshua Rogers
Closes #18966

diff --git a/lib/strdup.c b/lib/strdup.c
index 66fd7c60eb5f030532b364430d964bcb483d76af..3339e909ee794b6ba76f8a20f37f5a7f34e60f0a 100644 (file)
--- a/lib/strdup.c
+++ b/lib/strdup.c
@@ -111,7 +111,7 @@ void *Curl_memdup(const void *src, size_t length)
  ***************************************************************************/
 void *Curl_memdup0(const char *src, size_t length)
 {
-  char *buf = malloc(length + 1);
+  char *buf = (length < SIZE_MAX) ? malloc(length + 1) : NULL;
   if(!buf)
     return NULL;
   if(length) {