FAILED: patch "[PATCH] fs/remap: constrain dedupe of EOF blocks" failed to apply to 5.4-stable tree

FAILED: patch "[PATCH] fs/remap: constrain dedupe of EOF blocks" failed to apply to 5.4-stable tree

[gregkh]

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
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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@tu-darmstadt.de/
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))