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    Subject[PATCH 5.5 215/367] drm/rect: Avoid division by zero
    Date
    From: Ville Syrjälä <ville.syrjala@linux.intel.com>

    commit 433480c1afd44f3e1e664b85063d98cefeefa0ed upstream.

    Check for zero width/height destination rectangle in
    drm_rect_clip_scaled() to avoid a division by zero.

    Cc: stable@vger.kernel.org
    Fixes: f96bdf564f3e ("drm/rect: Handle rounding errors in drm_rect_clip_scaled, v3.")
    Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
    Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
    Cc: Daniel Vetter <daniel@ffwll.ch>
    Testcase: igt/kms_selftest/drm_rect_clip_scaled_div_by_zero
    Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20191122175623.13565-2-ville.syrjala@linux.intel.com
    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Reviewed-by: Benjamin Gaignard <benjamin.gaignard@st.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/drm_rect.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/drivers/gpu/drm/drm_rect.c
    +++ b/drivers/gpu/drm/drm_rect.c
    @@ -54,7 +54,12 @@ EXPORT_SYMBOL(drm_rect_intersect);

    static u32 clip_scaled(u32 src, u32 dst, u32 clip)
    {
    - u64 tmp = mul_u32_u32(src, dst - clip);
    + u64 tmp;
    +
    + if (dst == 0)
    + return 0;
    +
    + tmp = mul_u32_u32(src, dst - clip);

    /*
    * Round toward 1.0 when clipping so that we don't accidentally

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