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    Subject[PATCH 4.4 160/241] chardev: add additional check for minor range overlap
    Date
    [ Upstream commit de36e16d1557a0b6eb328bc3516359a12ba5c25c ]

    Current overlap checking cannot correctly handle
    a case which is baseminor < existing baseminor &&
    baseminor + minorct > existing baseminor + minorct.

    Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/char_dev.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/fs/char_dev.c b/fs/char_dev.c
    index 24b142569ca9b..d0655ca894816 100644
    --- a/fs/char_dev.c
    +++ b/fs/char_dev.c
    @@ -130,6 +130,12 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
    ret = -EBUSY;
    goto out;
    }
    +
    + if (new_min < old_min && new_max > old_max) {
    + ret = -EBUSY;
    + goto out;
    + }
    +
    }

    cd->next = *cp;
    --
    2.20.1


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