Patchwork getlogin_r: return early when linux sentinel value is set

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Submitter Jesse Hathaway
Date March 22, 2018, 7:30 p.m.
Message ID <CANSNSoWK7=NVnjsa4EFrcBwDSfJedNzMsYvKXD_e-M3k6zipRA@mail.gmail.com>
Download mbox | patch
Permalink /patch/26433/
State New
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Comments

Jesse Hathaway - March 22, 2018, 7:30 p.m.
On Thu, Mar 22, 2018 at 12:35 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> On Mär 21 2018, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>> +  if (uid == (uid_t) - 1)

fixed, attached

Patch

commit 7d60c6ab90d23bab16adc2809de95f99e84862d5
Author: Jesse Hathaway <jesse@mbuki-mvuki.org>
Date:   Fri Mar 16 10:46:50 2018 -0500

    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.

diff --git a/ChangeLog b/ChangeLog
index 3399e567b8..5d776d995f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@ 
+2018-03-20  Jesse Hathaway  <jesse@mbuki-mvuki.org>  (tiny change)
+
+	* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return
+	early when linux sentinel value is set.
+
 2018-03-20  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* manual/errno.texi (EOWNERDEAD, ENOTRECOVERABLE): Remove errno
diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c b/sysdeps/unix/sysv/linux/getlogin_r.c
index 73ea14c8f9..14587712a7 100644
--- a/sysdeps/unix/sysv/linux/getlogin_r.c
+++ b/sysdeps/unix/sysv/linux/getlogin_r.c
@@ -55,6 +55,15 @@  __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;
+    }
+
   struct passwd pwd;
   struct passwd *tpwd;
   int result = 0;