From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
overlayfs <linux-unionfs@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 03/10] ovl: check privs before decoding file handle
Date: Tue, 8 Dec 2020 15:49:25 +0200 [thread overview]
Message-ID: <CAOQ4uxhti+COYB3GhfMcPFwpfBRYQvr98oCO9wwS029W5e0A5g@mail.gmail.com> (raw)
In-Reply-To: <20201207163255.564116-4-mszeredi@redhat.com>
On Mon, Dec 7, 2020 at 6:36 PM Miklos Szeredi <mszeredi@redhat.com> wrote:
>
> CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in
> ovl_decode_real_fh() as well to prevent privilege escalation for
> unprivileged overlay mounts.
>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> ---
> fs/overlayfs/namei.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index a6162c4076db..82a55fdb1e7a 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -156,6 +156,9 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
> struct dentry *real;
> int bytes;
>
> + if (!capable(CAP_DAC_READ_SEARCH))
> + return NULL;
> +
If the mounter is not capable in init ns, ovl_check_origin() and
ovl_verify_index()
will not function as expected and this will break index and nfs export features.
So I think we need to also check capability in ovl_can_decode_fh(), to auto
disable those features.
Thanks,
Amir.
next prev parent reply other threads:[~2020-12-08 13:50 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 16:32 [PATCH v2 00/10] allow unprivileged overlay mounts Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 01/10] vfs: move cap_convert_nscap() call into vfs_setxattr() Miklos Szeredi
2020-12-09 1:53 ` James Morris
2021-01-01 17:35 ` Eric W. Biederman
2021-01-11 13:49 ` Miklos Szeredi
2021-01-12 0:14 ` Eric W. Biederman
2021-01-12 9:43 ` Miklos Szeredi
2021-01-12 10:04 ` Miklos Szeredi
2021-01-12 18:36 ` Eric W. Biederman
2021-01-12 18:49 ` Eric W. Biederman
2020-12-07 16:32 ` [PATCH v2 02/10] vfs: verify source area in vfs_dedupe_file_range_one() Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 03/10] ovl: check privs before decoding file handle Miklos Szeredi
2020-12-08 13:49 ` Amir Goldstein [this message]
2020-12-09 10:13 ` Miklos Szeredi
2020-12-09 16:20 ` Miklos Szeredi
2020-12-09 18:16 ` Amir Goldstein
2020-12-07 16:32 ` [PATCH v2 04/10] ovl: make ioctl() safe Miklos Szeredi
2020-12-08 11:11 ` Amir Goldstein
2020-12-10 15:18 ` Miklos Szeredi
2020-12-14 5:44 ` Amir Goldstein
2020-12-14 13:23 ` Miklos Szeredi
2020-12-14 14:47 ` Amir Goldstein
2020-12-09 1:57 ` James Morris
2020-12-10 15:19 ` Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 05/10] ovl: simplify file splice Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 06/10] ovl: user xattr Miklos Szeredi
2020-12-08 13:10 ` Amir Goldstein
2020-12-11 14:55 ` Miklos Szeredi
2020-12-14 5:13 ` Amir Goldstein
2020-12-07 16:32 ` [PATCH v2 07/10] ovl: do not fail when setting origin xattr Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 08/10] ovl: do not fail because of O_NOATIME Miklos Szeredi
2020-12-08 11:29 ` Amir Goldstein
2020-12-11 14:44 ` Miklos Szeredi
2020-12-14 5:49 ` Amir Goldstein
2020-12-07 16:32 ` [PATCH v2 09/10] ovl: do not get metacopy for userxattr Miklos Szeredi
2020-12-07 16:32 ` [PATCH v2 10/10] ovl: unprivieged mounts Miklos Szeredi
2020-12-08 10:27 ` [PATCH v2 00/10] allow unprivileged overlay mounts Tetsuo Handa
2020-12-10 8:56 ` John Johansen
2020-12-10 9:39 ` Miklos Szeredi
2020-12-15 11:03 ` John Johansen
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