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fs/remap: constrain dedupe of EOF blocks

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commit 5750676b64a561f7ec920d7c6ba130fc9c7378f3 upstream.

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: 1383a7ed67 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dave Chinner 2022-07-13 17:49:15 +10:00 committed by Greg Kroah-Hartman
parent 0581613df7
commit 14e63942d6
1 changed files with 2 additions and 1 deletions
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3
fs/remap_range.c
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@ -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))