GNU bug report logs - #23853
chmod can unset sticky bits using octet format

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: westlake <westlake2012 <at> videotron.ca>
To: bug-coreutils <at> gnu.org
Subject: chmod can unset sticky bits using octet format
Date: Sun, 26 Jun 2016 20:56:24 -0400

According to chmod's manpage,
"chmod preserves a directory's set-user-ID and set-group-ID bits unless 
you explicitly specify otherwise.  You can set or clear the bits with 
symbolic modes like u+s and g-s, and you can set (but not clear) the 
bits with a numeric mode."

contrary to documentation, chmod can otherwise clear sticky bits using 
the octet notation but by using a 5th octal

commands used,
mkdir abc
chmod u+s,g+s abc
chmod 0755 abc (no effect on the sticky bits)
chmod 00755 abc (sticky bits cleared using the 5th octal position)

Message #8 received at 23853 <at> debbugs.gnu.org (full text, mbox):

From: Eric Blake <eblake <at> redhat.com>
To: westlake <westlake2012 <at> videotron.ca>, 23853 <at> debbugs.gnu.org
Subject: Re: bug#23853: chmod can unset sticky bits using octet format
Date: Mon, 27 Jun 2016 08:13:20 -0600

[Message part 1 (text/plain, inline)]

On 06/26/2016 06:56 PM, westlake wrote:
> According to chmod's manpage,
> "chmod preserves a directory's set-user-ID and set-group-ID bits unless
> you explicitly specify otherwise.  You can set or clear the bits with
> symbolic modes like u+s and g-s, and you can set (but not clear) the
> bits with a numeric mode."
> 
> contrary to documentation, chmod can otherwise clear sticky bits using
> the octet notation but by using a 5th octal
> 
> commands used,
> mkdir abc
> chmod u+s,g+s abc
> chmod 0755 abc (no effect on the sticky bits)
> chmod 00755 abc (sticky bits cleared using the 5th octal position)

The behavior of the 5th octal to intentionally specify that the
otherwise leading 0 is intended to clear sticky bits is intentional, so
the only bug here is in the documentation for not making the intended
behavior more obvious.


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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Message #11 received at 23853 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: 23853 <at> debbugs.gnu.org
Subject: Re: bug#23853: chmod can unset sticky bits using octet format
Date: Sun, 28 Oct 2018 00:14:33 -0600

close 23853
stop

(triaging old bugs)

On 2016-06-27 8:13 a.m., Eric Blake wrote:
> On 06/26/2016 06:56 PM, westlake wrote:
>>
>> contrary to documentation, chmod can otherwise clear sticky bits using
>> the octet notation but by using a 5th octal
[...]
> The behavior of the 5th octal to intentionally specify that the
> otherwise leading 0 is intended to clear sticky bits is intentional, so
> the only bug here is in the documentation for not making the intended
> behavior more obvious.

With no further comments in 2 years,
I'm closing this bug.
Discussion can continue by replying to this thread.

-assaf

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