commit cc8a1620eb97ccddd337d157263c13c57b39ab71

Author: Jesse Hathaway <jesse@mbuki-mvuki.org>

Date:   Tue Mar 27 21:17:59 2018 +0000

    getlogin_r: return early when linux sentinel value is set

    When there is no login uid Linux sets /proc/self/loginid to the sentinel

    value of, (uid_t) -1. If this is set we can return early and avoid

    needlessly looking up the sentinel value in any configured nss

    databases.

    Checked on aarch64-linux-gnu.

            * sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return

            early when linux sentinel value is set.

    Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

Index: b/sysdeps/unix/sysv/linux/getlogin_r.c

===================================================================

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

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

@@ -54,6 +54,15 @@ __getlogin_r_loginuid (char *name, size_

 	  endp == uidbuf || *endp != '\0'))

     return -1;

+  /* If there is no login uid, linux sets /proc/self/loginid to the sentinel

+     value of, (uid_t) -1, so check if that value is set and return early to

+     avoid making unneeded nss lookups. */

+  if (uid == (uid_t) -1)

+    {

+      __set_errno (ENXIO);

+      return ENXIO;

+    }

+

   size_t buflen = 1024;

   char *buf = alloca (buflen);

   bool use_malloc = false;