wcsmbs: Fix data race in __wcsmbs_clone_conv [BZ #24584]

This also adds an overflow check and documents the synchronization
requirement in <gconv.h>.

1 files changed, 2 insertions, 0 deletions

diff --git a/iconv/gconv.h b/iconv/gconv.h
index 5ad26c06ac..7ce79bcbf6 100644
--- a/iconv/gconv.h
+++ b/iconv/gconv.h
@@ -86,6 +86,8 @@ struct __gconv_step
   struct __gconv_loaded_object *__shlib_handle;
   const char *__modname;
 
+  /* For internal use by glibc.  (Accesses to this member must occur
+     when the internal __gconv_lock mutex is acquired).  */
   int __counter;
 
   char *__from_name;