Use __pthread_attr_copy in mq_notify (bug 27896)

Make a deep copy of the pthread attribute object to remove a potential

use-after-free issue.

(cherry picked from commit 42d359350510506b87101cf77202fefcbfc790cb)

# Conflicts:

#	NEWS

diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c

index 3563e82cd4f4b552..c4091169306ffde8 100644

--- a/sysdeps/unix/sysv/linux/mq_notify.c

+++ b/sysdeps/unix/sysv/linux/mq_notify.c

@@ -135,8 +135,11 @@ helper_thread (void *arg)

 	    (void) __pthread_barrier_wait (&notify_barrier);

 	}

       else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED)

-	/* The only state we keep is the copy of the thread attributes.  */

-	free (data.attr);

+	{

+	  /* The only state we keep is the copy of the thread attributes.  */

+	  pthread_attr_destroy (data.attr);

+	  free (data.attr);

+	}

     }

   return NULL;

 }

@@ -257,8 +260,7 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification)

       if (data.attr == NULL)

 	return -1;

-      memcpy (data.attr, notification->sigev_notify_attributes,

-	      sizeof (pthread_attr_t));

+      __pthread_attr_copy (data.attr, notification->sigev_notify_attributes);

     }

   /* Construct the new request.  */

@@ -272,7 +274,10 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification)

   /* If it failed, free the allocated memory.  */

   if (__glibc_unlikely (retval != 0))

-    free (data.attr);

+    {

+      pthread_attr_destroy (data.attr);

+      free (data.attr);

+    }

   return retval;

 }