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From: Mark Fasheh <>
Subject: [PATCH 0/2] vfs: better dedupe permission check
Date: Fri, 11 May 2018 12:26:49 -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 readonly file
if the user owns it. Existing behavior is that we'll allow dedupe only

- 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 solution is simple - we allow dedupe of the target if the user
owns it. With that patch, a user can dedupe all of their files.

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


             reply	other threads:[~2018-05-11 19:27 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-11 19:26 Mark Fasheh [this message]
2018-05-11 19:26 ` [PATCH 1/2] vfs: allow dedupe of user owned read-only files Mark Fasheh
2018-05-11 23:58   ` Darrick J. Wong
2018-05-12  2:49   ` Adam Borowski
2018-05-13 18:16     ` Mark Fasheh
2018-05-13 20:50       ` Adam Borowski
2018-05-17 23:01         ` Mark Fasheh
2018-05-11 19:26 ` [PATCH 2/2] vfs: dedupe should return EPERM if permission is not granted Mark Fasheh
2018-05-12  0:06   ` Darrick J. Wong
2018-05-12  4:15     ` Amir Goldstein
2018-05-12  4:37     ` Duncan
2018-05-13 14:30     ` Adam Borowski
2018-05-13 18:21     ` Mark Fasheh
2018-05-13 18:26       ` Darrick J. Wong
2018-05-17  5:15         ` Zygo Blaxell
2018-05-17 23:03           ` Mark Fasheh
2018-05-14 14:58   ` David Sterba

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