On Wed, Sep 23, 2020 at 05:35:44PM -0500, Eric Sandeen wrote:
A bug existed in the XFS reflink code between v5.1 and v5.5 in which the mapping for a COW IO was not trimmed to the mapping of the COW extent that was found. This resulted in a too-short copy, and corruption of other files which shared the original extent.
(This happened only when extent size hints were set, which bypasses delalloc and led to this code path.)
This was (inadvertently) fixed upstream with
36adcbace24e "xfs: fill out the srcmap in iomap_begin"
and related patches which moved lots of this functionality to the iomap subsystem.
Hence, this is a -stable only patch, targeted to fix this corruption vector without other major code changes.
Fixes: 78f0cc9d55cb ("xfs: don't use delalloc extents for COW on files with extsize hints") Cc: stable@vger.kernel.org # 5.4.x Signed-off-by: Eric Sandeen sandeen@redhat.com
Looks good,
Reviewed-by: Christoph Hellwig hch@lst.de
and as Darrick said we'll want to wire up the reproducer for xfstests.