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From: Jann Horn <jannh@google.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>, Jann Horn <jannh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] fs: add a comment explaining how MNT_NS_INTERNAL affects mnt_may_suid()
Date: Mon, 4 Feb 2019 05:04:40 +0100
Message-ID: <CAG48ez0fP2-nyRNU54=hPYnFAc64zKCqFvRw0jw+MK49Gw-zOA@mail.gmail.com> (raw)
In-Reply-To: <20181121195859.10894-1-jannh@google.com>

On Wed, Nov 21, 2018 at 8:59 PM Jann Horn <jannh@google.com> wrote:
> commit 380cf5ba6b0a ("fs: Treat foreign mounts as nosuid"), in addition to
> the intended effect, also prevented suid execution of memfd files.
> (And I think that's a good change.)

Ping. Al, can you take this into your tree? fs/namespace.c is your stuff, right?


> Signed-off-by: Jann Horn <jannh@google.com>
> ---
>  fs/namespace.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index a7f91265ea67..e68488426e42 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -3400,6 +3400,9 @@ bool mnt_may_suid(struct vfsmount *mnt)
>          * prevents namespaces from trusting potentially unsafe
>          * suid/sgid bits, file caps, or security labels that originate
>          * in other namespaces.
> +        *
> +        * check_mnt() rejects MNT_NS_INTERNAL mounts; this means that suid
> +        * execution is blocked for files on internal mounts, e.g. memfds.
>          */
>         return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
>                current_in_userns(mnt->mnt_sb->s_user_ns);
> --
> 2.20.0.rc0.387.gc7a69e6b6c-goog
>

      reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-21 19:58 Jann Horn
2019-02-04  4:04 ` Jann Horn [this message]

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