[SOLVED] Perl failed to run on Linux

Issue

I have a simple Perl script as below:

#!/usr/bin/perl
print "###################################\n";

But when I try to execute it from the command line, I always see:

[root@testbox001 tmp]# ./def
-bash: ./def: Permission denied

The script is executable:

-rwxr-xr-x  1 root root    88 Dec 22 01:42 def

Also the bash and shebang:

[root@testbox001 tmp]# ls -l /usr/bin/bash
-rwxr-xr-x. 1 root root 1150560 Jun 20  2022 /usr/bin/bash
[root@testbox001 tmp]# ls -l /usr/bin/perl
-rwxr-xr-x. 2 root root 12752 Jan 17  2023 /usr/bin/perl
[root@testbox001 tmp]#

What are the causes?

I can only run it explicitly:

[root@testbox001 tmp]# /usr/bin/perl def
#########################################################
[root@testbox001 tmp]#

Solution

The program is found on the /tmp volume, which is mounted noexec.

$ mount | grep 'on /tmp '
/dev/sda3 on /tmp type ext4 (rw,nosuid,nodev,noexec,noatime,nodiratime,data=ordered)

This prevents programs on that volume from being executed.

$ /bin/echo foo
foo

$ cp /bin/echo /tmp/

$ /tmp/echo foo
-bash: /tmp/echo: Permission denied

The goal is to help neuter attacks.

Answered By - ikegami

Answer Checked By - Pedro (WPSolving Volunteer)