linux-kernel - Re: [GIT PULL] execve updates for v6.13-rc1 (take 2)

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Message-ID: <CAHk-=wi+_a9Y8DtEp2P9RnDCjn=gd4ym_5ddSTEAadAyzy1rkw@mail.gmail.com>
Date: Wed, 27 Nov 2024 17:59:53 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Kees Cook <kees@...nel.org>
Cc: linux-kernel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christophe JAILLET <christophe.jaillet@...adoo.fr>, "Eric W. Biederman" <ebiederm@...ssion.com>, 
	Nir Lichtman <nir@...htman.org>, Tycho Andersen <tandersen@...flix.com>, 
	Vegard Nossum <vegard.nossum@...cle.com>
Subject: Re: [GIT PULL] execve updates for v6.13-rc1 (take 2)

On Wed, 27 Nov 2024 at 16:53, Kees Cook <kees@...nel.org> wrote:
>
> On a related note, what do you think of using execveat's "pathname"
> argument as "comm" if AT_EMPTY_PATH is set? That'll give process
> launchers control over comm (which is what they want), and we can keep
> the dentry name fallback as proposed too?

That's not actually how AT_EMPTY_PATH works.

Yes, it's how AT_EMPTY_PATH *should* work, but despite the name,
AT_EMPTYH_PATH does not mean "path is empty".

It means "path *may* be empty - but if path isn't empty, it's a regular path".

IOW, what is going on is that POSIX required that an empty path be an
error. And AT_EMPTY_PATH is basically a "don't error out on an empty
path" flag, not a "path *is* empty" flag.

So if pathname exists and isn't empty, AT_EMPTY_PATH does nothing.

             Linus