archive mirror
 help / color / mirror / Atom feed
From: Mark Fasheh <>
	"Darrick J . Wong" <>,
	Adam Borowski <>
Subject: [PATCH v2 0/2] vfs: better dedupe permission check
Date: Fri, 18 May 2018 14:57:25 -0700	[thread overview]
Message-ID: <> (raw)


The following patches fix a couple of issues with the permission
check we do in vfs_dedupe_file_range().

The first patch expands our check to allow dedupe of a file if the
user owns it or otherwise would be allowed to write to it.

Current behavior is that we'll allow dedupe only if:

- the user is an admin (root)
- the user has the file open for write

This makes it impossible for a user to dedupe their own file set
unless they do it as root, or ensure that all files have write
permission. There's a couple of duperemove bugs open for this:

The other problem we have is also related to forcing the user to open
target files for write - A process trying to exec a file currently
being deduped gets ETXTBUSY. The answer (as above) is to allow them to
open the targets ro - root can already do this. There was a patch from
Adam Borowski to fix this back in 2016:

which I have incorporated into my changes.

The 2nd patch fixes our return code for permission denied to be
EPERM. For some reason we're returning EINVAL - I think that's
probably my fault. At any rate, we need to be returning something
descriptive of the actual problem, otherwise callers see EINVAL and
can't really make a valid determination of what's gone wrong.

This has also popped up in duperemove, mostly in the form of cryptic
error messages. Because this is a code returned to userspace, I did
check the other users of extent-same that I could find. Both 'bees'
and 'rust-btrfs' do the same as duperemove and simply report the error
(as they should).

The patches are also available in git:

git pull dedupe-perms


Changes from V1 to V2:
- Add inode_permission check as suggested by Adam Borowski
- V1 discussion:

             reply	other threads:[~2018-05-18 21:57 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-18 21:57 Mark Fasheh [this message]
2018-05-18 21:57 ` [PATCH v2 1/2] vfs: allow dedupe of user owned read-only files Mark Fasheh
2018-05-18 22:03   ` Darrick J. Wong
2018-05-18 22:06     ` Mark Fasheh
2018-05-18 21:57 ` [PATCH v2 2/2] vfs: dedupe should return EPERM if permission is not granted Mark Fasheh
2018-05-18 22:04   ` Darrick J. Wong
2018-05-18 22:08     ` Mark Fasheh
2018-05-21 12:35   ` David Sterba

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \

* 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).