From: Jesse Hathaway <jesse@mbuki-mvuki.org>
Date: Tue, 27 Mar 2018 21:17:59 +0000 (+0000)
Subject: getlogin_r: return early when linux sentinel value is set
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dadc309087c7acab517ed3e42546aa859ae9fb45;p=thirdparty%2Fglibc.git

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>
(cherry picked from commit cc8a1620eb97ccddd337d157263c13c57b39ab71)
---

diff --git a/ChangeLog b/ChangeLog
index 89ecd49d19a..670c6d94b8c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-27  Jesse Hathaway  <jesse@mbuki-mvuki.org>
+
+	* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return
+	early when linux sentinel value is set.
+
 2018-03-27  Andreas Schwab  <schwab@suse.de>
 
 	[BZ #23005]
diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c b/sysdeps/unix/sysv/linux/getlogin_r.c
index 84c51d0ecd1..7a814ea92f1 100644
--- 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_t namesize)
 	  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;