Date: Sat, 22 Apr 2000 06:07:06 -0600 (MDT)
From: "Nelson H. F. Beebe" <beebe@math.utah.edu>
Cc: beebe@math.utah.edu, sysstaff@math.utah.edu, othmer@math.utah.edu
Subject: gawk-3.0.4 and a GNU/Linux gotcha

Yesterday, I was assisting a colleague install some software on his
GNU/Linux machine for which uname -r reports 2.2.14.

A (mis)feature of this system, which I've never encountered before,
broke the build of one of my programs, and also of gawk-3.0.4.

Namely, the kernel will not execute anything that resides in /tmp,
though it will if the same script is in /usr/tmp!

% cat /tmp/foo.sh
#! /bin/sh
echo hello

ls -l /tmp/foo.sh
-rwxr-xr-x   1 othmer   math           22 Apr 21 10:34 /tmp/foo.sh*

% /tmp/foo.sh
bash: /tmp/foo.sh: Permission denied

% cp /tmp/foo.sh /usr/tmp

% /usr/tmp/foo.sh
hello

Thus, programs that do a temporary install in /tmp, as some of mine do
in order to run the validation suite, will fail.

gawk-3.0.4, and likely other gawk versions, hits this problem too. It
fails because test/poundbang starts with

#! /tmp/gawk -f

I tracked down where it comes from:

% grep /tmp /etc/fstab
/dev/hda3 /tmp ext2 rw,nosuid,noexec,nouser,auto,async,nodev 1 1
                              !!!!!!

Since this is done via a mount command, potentially ANY directory tree
could be mounted with noexec.