linux-kernel - Re: [PATCH] exec: fix the racy usage of fs_struct->in

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Message-ID: <20250325132136.GB7904@redhat.com>
Date: Tue, 25 Mar 2025 14:21:36 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: syzbot <syzbot+1c486d0b62032c82a968@...kaller.appspotmail.com>,
	brauner@...nel.org, kees@...nel.org, viro@...iv.linux.org.uk,
	jack@...e.cz, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] exec: fix the racy usage of fs_struct->in_exec

On 03/25, Mateusz Guzik wrote:
>
> On Tue, Mar 25, 2025 at 11:10 AM Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > On 03/24, Mateusz Guzik wrote:
> > >
> > > On Mon, Mar 24, 2025 at 7:28 PM Oleg Nesterov <oleg@...hat.com> wrote:
> > > >
> > > > So to me it would be better to have the trivial fix for stable,
> > > > exactly because it is trivially backportable. Then cleanup/simplify
> > > > this logic on top of it.
> > >
> > > So I got myself a crap testcase with a CLONE_FS'ed task which can
> > > execve and sanity-checked that suid is indeed not honored as expected.
> >
> > So you mean my patch can't fix the problem?
>
> No, I think the patch works.
>
> I am saying the current scheme is avoidably hard to reason about.

Ah, OK, thanks. Then I still think it makes more sense to do the
cleanups you propose on top of this fix.

But I leave this to you and other fs/ maintainers.

Oleg.