linux-hardening - Re: [PATCH] exec: fix up /proc/pid/comm in the execveat(AT_EMPTY

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Message-ID: <CAHk-=wgAVEbjFzhNpqvgTxKymCi6uE5UO7BzyB6ch7pDiUz+Yg@mail.gmail.com>
Date: Sat, 30 Nov 2024 13:34:06 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: Kees Cook <kees@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
	Tycho Andersen <tandersen@...flix.com>, Aleksa Sarai <cyphar@...har.com>, 
	Eric Biederman <ebiederm@...ssion.com>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] exec: fix up /proc/pid/comm in the execveat(AT_EMPTY_PATH)
 case

On Sat, 30 Nov 2024 at 12:28, Mateusz Guzik <mjguzik@...il.com> wrote:
>
> > +             /* The dentry name won't change while we hold the rcu read lock. */
> > +             __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name),
> > +                             true);
>
> This does not sound legit whatsoever as it would indicate all renames
> wait for rcu grace periods to end, which would be prettye weird.

Yes, the "won't change" should be "won't go away from under us".

          Linus