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References: <20181105182146.233025-1-salyzyn@android.com>
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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Mon, 5 Nov 2018 20:55:39 +0200
Message-ID: <CAOQ4uxiwxWDyz2yEfjcKdWK+iUEGKW4W=zoDKy2Z1xO0o7Zt9g@mail.gmail.com>
Subject: Re: [PATCH v6 0/2]
To:     Mark Salyzyn <salyzyn@android.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Jonathan Corbet <corbet@lwn.net>,
        Vivek Goyal <vgoyal@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        linux-doc@vger.kernel.org
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On Mon, Nov 5, 2018 at 8:22 PM Mark Salyzyn <salyzyn@android.com> wrote:
>
> overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh
>
> Assumption never checked, should fail if the mounter creds are not
> sufficient.
>
> overlayfs: override_creds=off option bypass creator_cred
>
> By default, all access to the upper, lower and work directories is the
> recorded mounter's MAC and DAC credentials.  The incoming accesses are
> checked against the caller's credentials.
>
> If the principles of least privilege are applied, the mounter's
> credentials might not overlap the credentials of the caller's when
> accessing the overlayfs filesystem.  For example, a file that a lower
> DAC privileged caller can execute, is MAC denied to the generally
> higher DAC privileged mounter, to prevent an attack vector.
>
> We add the option to turn off override_creds in the mount options; all
> subsequent operations after mount on the filesystem will be only the
> caller's credentials.  The module boolean parameter and mount option
> override_creds is also added as a presence check for this "feature",
> existence of /sys/module/overlay/parameters/overlay_creds
>
> Signed-off-by: Mark Salyzyn <salyzyn@android.com>
> Cc: Miklos Szeredi <miklos@szeredi.hu>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Amir Goldstein <amir73il@gmail.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Stephen Smalley <sds@tycho.nsa.gov>
> Cc: linux-unionfs@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
>
> v2:
> - Forward port changed attr to stat, resulting in a build error.
> - altered commit message.
>
> v3:
> - Change name from caller_credentials / creator_credentials to the
>   boolean override_creds.
> - Changed from creator to mounter credentials.
> - Updated and fortified the documentation.
> - Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS
>
> v4:
> - spelling and grammar errors in text
>
> v5:
> - beefed up the caveats in the Documentation
> - Is dependent on
>   "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh"
>   "overlayfs: check CAP_MKNOD before issuing vfs_whiteout"
> - Added prwarn when override_creds=off
>
> v6:
> - Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS.
> - Do better with the documentation, drop rationalizations.
> - pr_warn message adjusted to report consequences.

For future reference, the cover letter is meant for introduction,
not for concatenating all commit messages...
Not sure how you generated this text.
I think you were looking for git format-patch --cover.
Anyway, IMO, having the patch revision in the cover letter is sufficient
and you needn't bother with patch revision in every single patch, unless
there is a good reason.

Thanks,
Amir.