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Date:   Fri, 14 Jul 2023 00:06:02 +1000
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     Willy Tarreau <w@1wt.eu>
Cc:     Shuah Khan <shuah@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christian Brauner <brauner@kernel.org>,
        Dave Chinner <dchinner@redhat.com>,
        xu xin <cgel.zte@gmail.com>, Al Viro <viro@zeniv.linux.org.uk>,
        Stefan Roesch <shr@devkernel.io>,
        Zhihao Cheng <chengzhihao1@huawei.com>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Janis Danisevskis <jdanis@google.com>,
        Kees Cook <keescook@chromium.org>, stable@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <thomas@t-8ch.de>
Subject: Re: [PATCH] procfs: block chmod on /proc/thread-self/comm
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On 2023-07-13, Willy Tarreau <w@1wt.eu> wrote:
> +Cc Thomas Wei?schuh <thomas@t-8ch.de> as this seems quite related to
> his finding about /proc/self/net:
> 
>   https://lore.kernel.org/lkml/20230624-proc-net-setattr-v1-0-73176812adee@weissschuh.net/#b

Yeah I saw this patch and (along with an earlier discussion with
Christian on the topic of chmod on symlinks -- see [1]) lead us to find
that there were three other cases where this happens unintentionally:

 * /proc/self (on the symlink itself)
 * /proc/thread-self (on the symlink itself)
 * /proc/thread-self/comm

The first two will be fixed by [1] so fixing them isn't necessary.

[1]: https://lore.kernel.org/linux-fsdevel/20230712-vfs-chmod-symlinks-v2-1-08cfb92b61dd@kernel.org/

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>