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    Subject[PATCH 5.18 031/231] fs/remap: constrain dedupe of EOF blocks
    Date
    From: Dave Chinner <dchinner@redhat.com>

    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: 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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/remap_range.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/remap_range.c
    +++ b/fs/remap_range.c
    @@ -71,7 +71,8 @@ static int generic_remap_checks(struct f
    * 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))

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