From: Christian Brauner <brauner@kernel.org>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: Hyunchul Lee <hyc.lee@gmail.com>,
Namjae Jeon <linkinjeon@kernel.org>,
Steve French <smfrench@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v1] ksmbd: Fix user namespace mapping
Date: Thu, 29 Sep 2022 13:37:35 +0200 [thread overview]
Message-ID: <20220929113735.7k6fdu75oz4jvsvz@wittgenstein> (raw)
In-Reply-To: <20220929100447.108468-1-mic@digikod.net>
On Thu, Sep 29, 2022 at 12:04:47PM +0200, Mickaël Salaün wrote:
> A kernel daemon should not rely on the current thread, which is unknown
> and might be malicious. Before this security fix,
> ksmbd_override_fsids() didn't correctly override FS UID/GID which means
> that arbitrary user space threads could trick the kernel to impersonate
> arbitrary users or groups for file system access checks, leading to
> file system access bypass.
>
> This was found while investigating truncate support for Landlock:
> https://lore.kernel.org/r/CAKYAXd8fpMJ7guizOjHgxEyyjoUwPsx3jLOPZP=wPYcbhkVXqA@mail.gmail.com
>
> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
> Cc: Hyunchul Lee <hyc.lee@gmail.com>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Steve French <smfrench@gmail.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20220929100447.108468-1-mic@digikod.net
> ---
I think this is ok. The alternative would probably be to somehow use a
relevant userns when struct ksmbd_user is created when the session is
established. But these are deeper ksmbd design questions. The fix
proposed here itself seems good.
next prev parent reply other threads:[~2022-09-29 11:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-29 10:04 [PATCH v1] ksmbd: Fix user namespace mapping Mickaël Salaün
2022-09-29 11:37 ` Christian Brauner [this message]
2022-09-29 12:18 ` Mickaël Salaün
2022-09-29 13:08 ` Christian Brauner
2022-09-29 12:38 ` Namjae Jeon
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