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Re: [PATCH] getlogin_r: return early when linux sentinel value is set
- From: Jesse Hathaway <jesse at mbuki-mvuki dot org>
- To: Andreas Schwab <schwab at linux-m68k dot org>
- Cc: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, libc-alpha at sourceware dot org
- Date: Wed, 21 Mar 2018 16:27:56 -0500
- Subject: Re: [PATCH] getlogin_r: return early when linux sentinel value is set
- References: <CANSNSoWLXfsYq6kP0niyP8r25S=S1uTKN=+46xnC_SPLBmKXhQ@mail.gmail.com> <73b04097-ef36-b597-4f7c-2e73c6eb9fa3@linaro.org> <CANSNSoVxHOAM9XZx5ghighXLmXQzSvBfy4xp_FU8=_+U2ZXk8Q@mail.gmail.com> <877eq6ppkw.fsf@linux-m68k.org>
On Tue, Mar 20, 2018 at 1:30 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> Depends on whether you want the linux __getlogin_r to fall back to the
> generic __getlogin_r.
Thanks, updated patch below:
>From 04a50b5ee857aa33e1527d70f0676b6daf5a036c Mon Sep 17 00:00:00 2001
From: Jesse Hathaway <jesse@mbuki-mvuki.org>
Date: Fri, 16 Mar 2018 10:46:50 -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, (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..1ceff1c094 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..1f90c1ca2d 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;