Re: [PATCH v2 00/25] fs: fixes for serious clone/dedupe problems

Dave Chinner
2018-10-10T01:02:08Z

On Tue, Oct 09, 2018 at 05:10:38PM -0700, Darrick J. Wong wrote:
> Hi all,
>
> Dave, Eric, and I have been chasing a stale data exposure bug in the XFS
> reflink implementation, and tracked it down to reflink forgetting to do
> some of the file-extending activities that must happen for regular
> writes.
>
> We then started auditing the clone, dedupe, and copyfile code and
> realized that from a file contents perspective, clonerange isn't any
> different from a regular file write. Unfortunately, we also noticed
> that *unlike* a regular write, clonerange skips a ton of overflow
> checks, such as validating the ranges against s_maxbytes, MAX_NON_LFS,
> and RLIMIT_FSIZE. We also observed that cloning into a file did not
> strip security privileges (suid, capabilities) like a regular write
> would. I also noticed that xfs and ocfs2 need to dump the page cache
> before remapping blocks, not after.
>
> In fixing the range checking problems I also realized that both dedupe
> and copyfile tell userspace how much of the requested operation was
> acted upon. Since the range validation can shorten a clone request (or
> we can ENOSPC midway through), we might as well plumb the short
> operation reporting back through the VFS indirection code to userspace.
>
> So, here's the whole giant pile of patches[1] that fix all the problems.
> The patch "generic: test reflink side effects" recently sent to fstests
> exercises the fixes in this series. Tests are in [2].

Can you rebase this on the for-next branch on the xfs tree which
already contains some of the initial fixes in the series and a
couple of other reflink/dedupe data corruption fixes? I'm planning
on pushing them to Greg tomorrow, so you'll have to do this soon
anyway....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com