From: ebiederm@xmission.com (Eric W. Biederman)
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Miklos Szeredi <mszeredi@redhat.com>,
linux-fsdevel@vger.kernel.org,
overlayfs <linux-unionfs@vger.kernel.org>,
LSM <linux-security-module@vger.kernel.org>,
linux-kernel@vger.kernel.org,
"Serge E. Hallyn" <serge@hallyn.com>, <linux-api@vger.kernel.org>
Subject: Re: [PATCH v2 01/10] vfs: move cap_convert_nscap() call into vfs_setxattr()
Date: Tue, 12 Jan 2021 12:49:12 -0600 [thread overview]
Message-ID: <87blduf0t3.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <87bldugfxx.fsf@x220.int.ebiederm.org> (Eric W. Biederman's message of "Tue, 12 Jan 2021 12:36:58 -0600")
ebiederm@xmission.com (Eric W. Biederman) writes:
> So there is the basic question do we want to read the raw bytes on disk
> or do we want to return something meaningful to the reader. As the
> existing tools use the xattr interface to set/clear fscaps returning
> data to user space rather than raw bytes seems the perfered interface.
>
> My ideal semantics would be:
>
> - If current_user_ns() == sb->s_user_ns return the raw data.
>
> I don't know how to implement this first scenario while permitting
> stacked filesystems.
After a little more thought I do.
In getxattr if the get_cap method is not implemented by the
filesystem if current_user_ns() == sb->s_user_ns simply treat it as
an ordinary xattr read/write.
Otherwise call vfs_get_cap and translate the result as described
below.
The key point of this is it allows for seeing what is actually on
disk (when it is not confusing).
> - Calculate the cpu_vfs_cap_data as get_vfs_caps_from_disk does.
> That gives the meaning of the xattr.
>
> - If "from_kuid(current_userns(), krootid) == 0" return a v2 cap.
>
> - If "rootid_owns_currentns()" return a v2 cap.
>
> - Else return an error. Probably a permission error.
>
> The fscap simply can not make sense to the user if the rootid does not
> map. Return a v2 cap would imply that the caps are present on the
> executable (in the current context) which they are not.
Eric
next prev parent reply other threads:[~2021-01-12 18:51 UTC|newest]
Thread overview: 39+ 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 [this message]
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
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
2020-12-07 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87blduf0t3.fsf@x220.int.ebiederm.org \
--to=ebiederm@xmission.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=mszeredi@redhat.com \
--cc=serge@hallyn.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).