[src/trunk]: src/lib/libc/sys document a hack about setuid programs and fd 0, ...

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/dcc51d441c0b
branches:  trunk
changeset: 535150:dcc51d441c0b
user:      yamt <yamt%NetBSD.org@localhost>
date:      Sun Aug 11 10:27:49 2002 +0000

description:
document a hack about setuid programs and fd 0, 1 and 2.
from OpenBSD.

diffstat:

 lib/libc/sys/execve.2 |  10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diffs (24 lines):

diff -r 07b412fde6c4 -r dcc51d441c0b lib/libc/sys/execve.2
--- a/lib/libc/sys/execve.2     Sun Aug 11 09:39:10 2002 +0000
+++ b/lib/libc/sys/execve.2     Sun Aug 11 10:27:49 2002 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: execve.2,v 1.22 2002/02/08 01:28:17 ross Exp $
+.\"    $NetBSD: execve.2,v 1.23 2002/08/11 10:27:49 yamt Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -126,6 +126,14 @@
 Descriptors that remain open are unaffected by
 .Fn execve .
 .Pp
+In the case of a new setuid or setgid executable being executed, if
+file descriptors 0, 1, or 2 (representing stdin, stdout, and stderr)
+are currently unallocated, these descriptors will be opened to point to
+some system file like
+.Pa /dev/null .
+The intent is to ensure these descriptors are not unallocated, since
+many libraries make assumptions about the use of these 3 file descriptors.
+.Pp
 Signals set to be ignored in the calling process are set to be ignored in
 the
 new process. Signals which are set to be caught in the calling process image