The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5750676b64a561f7ec920d7c6ba130fc9c7378f3 Mon Sep 17 00:00:00 2001 From: Dave Chinner dchinner@redhat.com Date: Wed, 13 Jul 2022 17:49:15 +1000 Subject: [PATCH] fs/remap: constrain dedupe of EOF blocks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

If dedupe of an EOF block is not constrainted to match against only other EOF blocks with the same EOF offset into the block, it can match against any other block that has the same matching initial bytes in it, even if the bytes beyond EOF in the source file do not match.

Fix this by constraining the EOF block matching to only match against other EOF blocks that have identical EOF offsets and data. This allows "whole file dedupe" to continue to work without allowing eof blocks to randomly match against partial full blocks with the same data.

Reported-by: Ansgar Lößer ansgar.loesser@tu-darmstadt.de Fixes: 1383a7ed6749 ("vfs: check file ranges before cloning files") Link: https://lore.kernel.org/linux-fsdevel/a7c93559-4ba1-df2f-7a85-55a143696405@t... Signed-off-by: Dave Chinner dchinner@redhat.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/fs/remap_range.c b/fs/remap_range.c index e112b5424cdb..881a306ee247 100644 --- a/fs/remap_range.c +++ b/fs/remap_range.c @@ -71,7 +71,8 @@ static int generic_remap_checks(struct file *file_in, loff_t pos_in, * Otherwise, make sure the count is also block-aligned, having * already confirmed the starting offsets' block alignment. */ - if (pos_in + count == size_in) { + if (pos_in + count == size_in && + (!(remap_flags & REMAP_FILE_DEDUP) || pos_out + count == size_out)) { bcount = ALIGN(size_in, bs) - pos_in; } else { if (!IS_ALIGNED(count, bs))