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    Subject[PATCH 5.4 86/92] iomap: Fix pipe page leakage during splicing
    Date
    From: Jan Kara <jack@suse.cz>

    commit 419e9c38aa075ed0cd3c13d47e15954b686bcdb6 upstream.

    When splicing using iomap_dio_rw() to a pipe, we may leak pipe pages
    because bio_iov_iter_get_pages() records that the pipe will have full
    extent worth of data however if file size is not block size aligned
    iomap_dio_rw() returns less than what bio_iov_iter_get_pages() set up
    and splice code gets confused leaking a pipe page with the file tail.

    Handle the situation similarly to the old direct IO implementation and
    revert iter to actually returned read amount which makes iter consistent
    with value returned from iomap_dio_rw() and thus the splice code is
    happy.

    Fixes: ff6a9292e6f6 ("iomap: implement direct I/O")
    CC: stable@vger.kernel.org
    Reported-by: syzbot+991400e8eba7e00a26e1@syzkaller.appspotmail.com
    Signed-off-by: Jan Kara <jack@suse.cz>
    Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
    Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/iomap/direct-io.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    --- a/fs/iomap/direct-io.c
    +++ b/fs/iomap/direct-io.c
    @@ -497,8 +497,15 @@ iomap_dio_rw(struct kiocb *iocb, struct
    }
    pos += ret;

    - if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
    + if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
    + /*
    + * We only report that we've read data up to i_size.
    + * Revert iter to a state corresponding to that as
    + * some callers (such as splice code) rely on it.
    + */
    + iov_iter_revert(iter, pos - dio->i_size);
    break;
    + }
    } while ((count = iov_iter_count(iter)) > 0);
    blk_finish_plug(&plug);


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