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getlogin_r: return early when linux sentinel value is set

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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 cc8a1620eb)
This commit is contained in:
Jesse Hathaway 2018-03-27 21:17:59 +00:00 committed by Dmitry V. Levin
parent 1a90f09f24
commit a8a7d4c5d8
2 changed files with 14 additions and 0 deletions
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ChangeLog
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@ -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]

9
sysdeps/unix/sysv/linux/getlogin_r.c
View File

@ -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;