From dadc309087c7acab517ed3e42546aa859ae9fb45 Mon Sep 17 00:00:00 2001 From: Jesse Hathaway Date: Tue, 27 Mar 2018 21:17:59 +0000 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. 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 (cherry picked from commit cc8a1620eb97ccddd337d157263c13c57b39ab71) --- ChangeLog | 5 +++++ sysdeps/unix/sysv/linux/getlogin_r.c | 9 +++++++++ 2 files changed, 14 insertions(+) diff --git a/ChangeLog b/ChangeLog index 89ecd49d19a..670c6d94b8c 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2018-03-27 Jesse Hathaway + + * sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return + early when linux sentinel value is set. + 2018-03-27 Andreas Schwab [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; -- 2.47.2