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

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Message-ID: <CAHk-=wj6kh-N4n1zZEzJx+eCO_Wf2JGOGqb_Ndi6oo2QiEMmCQ@mail.gmail.com>
Date: Wed, 20 Nov 2024 18:51:12 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Kees Cook <kees@...nel.org>, linux-kernel@...r.kernel.org, 
	Christophe JAILLET <christophe.jaillet@...adoo.fr>, Dan Carpenter <dan.carpenter@...aro.org>, 
	"Eric W. Biederman" <ebiederm@...ssion.com>, Nir Lichtman <nir@...htman.org>, 
	syzbot+03e1af5c332f7e0eb84b@...kaller.appspotmail.com, 
	Tycho Andersen <tandersen@...flix.com>, Vegard Nossum <vegard.nossum@...cle.com>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>
Subject: Re: [GIT PULL] execve updates for v6.13-rc1

On Wed, 20 Nov 2024 at 18:36, Al Viro <viro@...iv.linux.org.uk> wrote:
> > If you want to be extra careful, you might surround it with a
> >
> >         read_seqbegin_or_lock(&rename_lock, &seq);
>
> What for?

Yeah, probably no good reason.

>         char name[something];
>
>         sprintf(name, "%*pD", sizeof(name) - 1, file);
>
> and be done with that...

I think you might as well just do the much cheaper

        rcu_read_lock();
        strscpy_pad(tsk->comm, sizeof(tsk->comm),
                smp_read_acquire(&dentry->d_name.name);
        rcu_read_unlock();

and be done with it. Using snprintf() on tsk->comm[] violates all the
rules we have for it, and while our rules aren't great, *that* one we
shouldn't do.

                 Linus