From: "mame (Yusuke Endoh)" <mame@...>
Date: 2013-02-20T15:28:12+09:00
Subject: [ruby-core:52565] [ruby-trunk - Bug #7879] File.readable? fails when ruby runs as root


Issue #7879 has been updated by mame (Yusuke Endoh).


kosaki (Motohiro KOSAKI) wrote:
> When run as root, access(2) ignore permission and always return success. That's UNIX filesystem semantics.
> In the other words, this is completely your script bug.

Wow...

> You need specific concern when opening /proc, /sys and similar pseudo filesystem's file.

Out of curiosity, what should we concern concretely?  Should we assume File.readable? as a hint?

-- 
Yusuke Endoh <mame@tsg.ne.jp>

----------------------------------------
Bug #7879: File.readable? fails when ruby runs as root
https://bugs.ruby-lang.org/issues/7879#change-36653

Author: balbi (Feliple Balbi)
Status: Rejected
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: core
Target version: 2.1.0
ruby -v: ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]


I have the following script to find sysfs (linux) files which are readable but throw an exception when read:

Dir.glob("/sys/**/*").each do |file|
        next if File.directory?(file)

        if File.world_writable?(file)
                puts "#{file} is world-writable"
        end

        if File.readable?(file)
                begin
                        File.open(file) { |f|
                                result = f.readline
                        }
                rescue EOFError
                        nil
                rescue => e
                        puts e.message
                end
        end
end

If I run as a normal user, it works just fine, but when I run as root, even for files which are write only (chmod 200), File.readable?(f) will return true which makes my script fail. I have also tried File.readable_real? but it has the same outcome.


-- 
http://bugs.ruby-lang.org/