From: "Serge E. Hallyn" <email@example.com>
To: "Eric W. Biederman" <firstname.lastname@example.org>
Cc: "Serge E. Hallyn" <email@example.com>,
Miklos Szeredi <firstname.lastname@example.org>,
Christian Brauner <email@example.com>
Subject: Re: [PATCH 2/2] security.capability: fix conversions on getxattr
Date: Fri, 29 Jan 2021 20:06:52 -0600 [thread overview]
Message-ID: <20210130020652.GB7163@mail.hallyn.com> (raw)
On Fri, Jan 29, 2021 at 04:55:29PM -0600, Eric W. Biederman wrote:
> "Serge E. Hallyn" <firstname.lastname@example.org> writes:
> > On Thu, Jan 28, 2021 at 02:19:13PM -0600, Eric W. Biederman wrote:
> >> "Serge E. Hallyn" <email@example.com> writes:
> >> > On Tue, Jan 19, 2021 at 07:34:49PM -0600, Eric W. Biederman wrote:
> >> >> Miklos Szeredi <firstname.lastname@example.org> writes:
> >> >>
> >> >> > If a capability is stored on disk in v2 format cap_inode_getsecurity() will
> >> >> > currently return in v2 format unconditionally.
> >> >> >
> >> >> > This is wrong: v2 cap should be equivalent to a v3 cap with zero rootid,
> >> >> > and so the same conversions performed on it.
> >> >> >
> >> >> > If the rootid cannot be mapped v3 is returned unconverted. Fix this so
> >> >> > that both v2 and v3 return -EOVERFLOW if the rootid (or the owner of the fs
> >> >> > user namespace in case of v2) cannot be mapped in the current user
> >> >> > namespace.
> >> >>
> >> >> This looks like a good cleanup.
> >> >
> >> > Sorry, I'm not following. Why is this a good cleanup? Why should
> >> > the xattr be shown as faked v3 in this case?
> >> If the reader is in &init_user_ns. If the filesystem was mounted in a
> >> user namespace. Then the reader looses the information that the
> > Can you be more precise about "filesystem was mounted in a user namespace"?
> > Is this a FUSE thing, the fs is marked as being mounted in a non-init userns?
> > If that's a possible case, then yes that must be represented as v3. Using
> > is_v2header() may be the simpler way to check for that, but the more accurate
> > check would be "is it v2 header and mounted by init_user_ns".
> I think the filesystems current relevant are fuse,overlayfs,ramfs,tmpfs.
> > Basically yes, in as many cases as possible we want to just give a v2
> > cap because more userspace knows what to do with that, but a non-init-userns
> > mounted fs which provides a v2 fscap should have it represented as v3 cap
> > with rootid being the kuid that owns the userns.
> That is the case we that is being fixed in the patch.
> > Or am I still thinking wrongly? Wouldn't be entirely surprised :)
> No you got it.
So then can we make faking a v3 gated on whether
sb->s_user_ns != &init_user_ns ?
next prev parent reply other threads:[~2021-01-30 10:09 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 16:22 [PATCH 0/2] capability conversion fixes Miklos Szeredi
2021-01-19 16:22 ` [PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability Miklos Szeredi
2021-01-19 21:06 ` Eric W. Biederman
2021-01-20 7:52 ` Miklos Szeredi
2021-01-22 16:04 ` Tyler Hicks
2021-01-22 18:31 ` Tyler Hicks
2021-01-25 13:25 ` Miklos Szeredi
2021-01-25 13:46 ` Miklos Szeredi
2021-01-26 1:52 ` Tyler Hicks
2021-01-19 16:22 ` [PATCH 2/2] security.capability: fix conversions on getxattr Miklos Szeredi
2021-01-20 1:34 ` Eric W. Biederman
2021-01-20 7:58 ` Miklos Szeredi
2021-01-28 16:58 ` Serge E. Hallyn
2021-01-28 20:19 ` Eric W. Biederman
2021-01-28 20:38 ` Miklos Szeredi
2021-01-28 20:49 ` Eric W. Biederman
[not found] ` <20210129154839.GC1130@mail.hallyn.com>
2021-01-29 22:55 ` Eric W. Biederman
2021-01-30 2:06 ` Serge E. Hallyn [this message]
2021-01-31 18:14 ` Eric W. Biederman
[not found] ` <CAJfpegt34fO8tUw8R2_ZxxKHBdBO_-quf+-f3N8aZmS=1oRdvQ@mail.gmail.com>
[not found] ` <20210129153807.GA1130@mail.hallyn.com>
2021-01-29 23:11 ` Eric W. Biederman
2021-01-30 2:04 ` Serge E. Hallyn
2021-01-20 19:37 ` kernel test robot
2021-01-20 21:08 ` kernel test robot
2021-01-19 21:10 ` [PATCH 0/2] capability conversion fixes Eric W. Biederman
2021-01-20 7:39 ` Miklos Szeredi
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