From: Miklos Szeredi <miklos@szeredi.hu>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Vivek Goyal <vgoyal@redhat.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
Mark Salyzyn <salyzyn@android.com>,
Paul Moore <paul@paul-moore.com>,
linux-kernel@vger.kernel.org,
overlayfs <linux-unionfs@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, selinux@vger.kernel.org,
Daniel J Walsh <dwalsh@redhat.com>
Subject: Re: overlayfs access checks on underlying layers
Date: Thu, 29 Nov 2018 20:47:22 +0100 [thread overview]
Message-ID: <CAJfpegv6y56k1-Tewu-Pu3x1W75LL6qYB6Hb6=n+2BJoNfEigA@mail.gmail.com> (raw)
In-Reply-To: <6b125e8e-413f-f8e6-c7ae-50f7235c8960@tycho.nsa.gov>
On Thu, Nov 29, 2018 at 5:14 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:
> Possibly I misunderstood you, but I don't think we want to copy-up on
> permission denial, as that would still allow the mounter to read/write
> special files or execute regular files to which it would normally be
> denied access, because the copy would inherit the context specified by
> the mounter in the context mount case. It still represents an
> escalation of privilege for the mounter. In contrast, the copy-up on
> write behavior does not allow the mounter to do anything it could not do
> already (i.e. read from the lower, write to the upper).
Let's get this straight: when file is copied up, it inherits label
from context=, not from label of lower file?
Next question: permission to change metadata is tied to permission to
open? Is it possible that open is denied, but metadata can be
changed?
DAC model allows this: metadata change is tied to ownership, not mode
bits. And different capability flag.
If the same is true for MAC, then the pre-v4.20-rc1 is already
susceptible to the privilege escalation you describe, right?
Thanks,
Miklos
next prev parent reply other threads:[~2018-11-29 19:47 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 19:55 overlayfs access checks on underlying layers Miklos Szeredi
2018-11-27 19:58 ` Miklos Szeredi
2018-11-27 21:05 ` Vivek Goyal
2018-11-28 10:00 ` Miklos Szeredi
2018-11-28 17:03 ` Vivek Goyal
2018-11-28 19:34 ` Stephen Smalley
2018-11-28 20:24 ` Miklos Szeredi
2018-11-28 21:46 ` Stephen Smalley
2018-11-29 11:04 ` Miklos Szeredi
2018-11-29 13:49 ` Vivek Goyal
2019-03-04 17:01 ` Mark Salyzyn
2019-03-04 17:56 ` Casey Schaufler
2019-03-04 18:44 ` Stephen Smalley
2019-03-04 19:21 ` Amir Goldstein
2018-11-29 16:16 ` Stephen Smalley
2018-11-29 16:22 ` Stephen Smalley
2018-11-29 19:47 ` Miklos Szeredi [this message]
2018-11-29 21:03 ` Stephen Smalley
2018-11-29 21:19 ` Stephen Smalley
2018-12-04 13:32 ` Miklos Szeredi
2018-12-04 14:30 ` Stephen Smalley
2018-12-04 14:45 ` Miklos Szeredi
2018-12-04 15:35 ` Stephen Smalley
2018-12-04 15:39 ` Miklos Szeredi
2018-12-11 15:50 ` Paul Moore
2018-12-04 15:15 ` Vivek Goyal
2018-12-04 15:22 ` Vivek Goyal
2018-12-04 15:31 ` Miklos Szeredi
2018-12-04 15:42 ` Vivek Goyal
2018-12-04 16:05 ` Stephen Smalley
2018-12-04 16:17 ` Vivek Goyal
2018-12-04 16:49 ` Stephen Smalley
2018-12-05 13:43 ` Vivek Goyal
2018-12-06 20:26 ` Stephen Smalley
2018-12-11 21:48 ` Vivek Goyal
2018-12-12 14:51 ` Stephen Smalley
2018-12-13 14:58 ` Vivek Goyal
2018-12-13 16:12 ` Stephen Smalley
2018-12-13 18:54 ` Vivek Goyal
2018-12-13 20:09 ` Stephen Smalley
2018-12-13 20:26 ` Vivek Goyal
2018-12-04 15:42 ` Stephen Smalley
2018-12-04 16:15 ` Vivek Goyal
2018-11-29 22:22 ` Daniel Walsh
2018-12-03 23:27 ` Paul Moore
2018-12-04 14:43 ` Stephen Smalley
2018-12-04 23:01 ` Paul Moore
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