linux-kernel - Re: [PATCH v2] kernel/fork: stop playing lockless games for exe

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Message-ID: <20230814181114.GD17738@redhat.com>
Date:   Mon, 14 Aug 2023 20:11:15 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        brauner@...nel.org, ebiederm@...ssion.com, david@...hat.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org, koct9i@...il.com,
        dave@...olabs.net
Subject: Re: [PATCH v2] kernel/fork: stop playing lockless games for exe_file
 replacement

On 08/14, Mateusz Guzik wrote:
>
> However, fe69d560b5bd ("kernel/fork: always deny write access to current
> MM exe_file") added a semaphore up/down cycle to synchronize the state
> of exe_file against fork, defeating the point of the original change.

Agreed,

> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
> ---
>  fs/exec.c     |  4 ++--
>  kernel/fork.c | 22 +++++++++-------------
>  2 files changed, 11 insertions(+), 15 deletions(-)

Acked-by: Oleg Nesterov <oleg@...hat.com>