[ruby-core:52507] [ruby-trunk - Bug #7879][Rejected] File.readable? fails when ruby runs as root

Issue #7879 has been updated by kosaki (Motohiro KOSAKI).

Status changed from Open to Rejected

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.

You need specific concern when opening /proc, /sys and similar pseudo filesystem's file.
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Bug #7879: File.readable? fails when ruby runs as root
https://bugs.ruby-lang.org/issues/7879#change-36583

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.


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