Re: [PATCH 1/2] builddeb: Fix rootless build in setuid/setgid directory

[Sven Joachim <svenjoac@gmx.de>]

On 2020-10-28 15:00 +0900, Masahiro Yamada wrote:

> On Tue, Oct 27, 2020 at 4:32 AM Sven Joachim <svenjoac@gmx.de> wrote:
>>
>> Building 5.10-rc1 in a setgid directory failed with the following
>> error:
>>
>> dpkg-deb: error: control directory has bad permissions 2755 (must be
>> >=0755 and <=0775)
>>
>> When building with fakeroot, the earlier chown call would have removed
>> the setgid bits, but in a rootless build they remain.
>>
>
>
> Applied to linux-kbuild. Thanks.

I don't see it there, have you pushed it out yet?

> I agreed with "g-s" but was not sure about "u-s"
> because nothing is explained about setuid,
> and the setuid bit against directories seems to have no effect.
>
>
>
>
>
> It was interesting to read this article:
> https://superuser.com/questions/471844/why-is-setuid-ignored-on-directories
>
>
>
> Also, it is summarized in the wikipedia
> https://en.wikipedia.org/wiki/Setuid#setuid_and_setgid_on_directories
>
> "The setuid permission set on a directory is ignored on most UNIX and
> Linux systems.[citation needed] However FreeBSD can be configured to
> interpret setuid in a manner similar to setgid, in which case it
> forces all files and sub-directories created in a directory to be
> owned by that directory's owner - a simple form of inheritance.[5]
> This is generally not needed on most systems derived from BSD, since
> by default directories are treated as if their setgid bit is always
> set, regardless of the actual value. As is stated in open(2), "When a
> new file is created it is given the group of the directory which
> contains it.""
>
>
> After all, I am convinced that it would not hurt to do "u-s"
> although I have never tested kernel builds on FreeBSD.

Agreed, setuid directories should not end up in the .deb files even if
that bit does currently nothing.

Cheers,
       Sven