Fix environment traversal when an envvar value is empty

The condition when the value of an envvar is empty (not just '\0'),
the loop in tunables_init gets stuck infinitely because envp is not
incremented.  Fix that by always incrementing envp in the loop.

Added test case (tst-empty-env.c) verifies the fix when the source is
configured with --enable-hardcoded-path-in-tests, thanks Josh Stone for
providing the test case.  Verified on x86_64.

	* elf/dl-tunables (get_next_env): Always advance envp.
	* stdlib/tst-empty-env.c: New test case.
	* stdlib/Makefile (tests): Use it.

1 files changed, 2 insertions, 2 deletions

diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index e0119d17ed..ba5246a099 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -80,7 +80,7 @@ get_next_env (char **envp, char **name, size_t *namelen, char **val)
 {
   while (envp != NULL && *envp != NULL)
     {
-      char *envline = *envp;
+      char *envline = *envp++;
       int len = 0;
 
       while (envline[len] != '\0' && envline[len] != '=')
@@ -94,7 +94,7 @@ get_next_env (char **envp, char **name, size_t *namelen, char **val)
       *namelen = len;
       *val = &envline[len + 1];
 
-      return ++envp;
+      return envp;
     }
 
   return NULL;