From: Mark Fasheh <firstname.lastname@example.org>
Cc: email@example.com, firstname.lastname@example.org,
"Darrick J . Wong" <email@example.com>,
Adam Borowski <firstname.lastname@example.org>
Subject: [PATCH v2 0/2] vfs: better dedupe permission check
Date: Fri, 18 May 2018 14:57:25 -0700 [thread overview]
Message-ID: <email@example.com> (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 https://github.com/markfasheh/linux dedupe-perms
Changes from V1 to V2:
- Add inode_permission check as suggested by Adam Borowski
- V1 discussion: https://marc.info/?l=linux-xfs&m=152606684017965&w=2
next 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
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