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[PATCH] getlogin_r: return early when linux sentinel value is set
- From: Jesse Hathaway <jesse at mbuki-mvuki dot org>
- To: libc-alpha at sourceware dot org
- Date: Fri, 16 Mar 2018 11:18:38 -0500
- Subject: [PATCH] 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 4294967295. If this is set we can return early and avoid
needlessly looking up the sentinel value in any configured nss
databases.
diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c
b/sysdeps/unix/sysv/linux/getlogin_r.c
index 73ea14c8f9..43f55a2188 100644
--- a/sysdeps/unix/sysv/linux/getlogin_r.c
+++ b/sysdeps/unix/sysv/linux/getlogin_r.c
@@ -55,6 +55,12 @@ __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 4294967295, so check if the value is set and return early to
+ avoid making unneeded nss lookups. */
+ if (uid == 4294967295)
+ return ENXIO;
+
struct passwd pwd;
struct passwd *tpwd;
int result = 0;