lima: avoid crash with negative viewport values

The viewport value computations done in lima_set_viewport_states
can result in a negative value for viewport.
These could end up converted to unsigned values in
lima_clip_scissor_to_viewport causing crashes from invalid
scissor commands.
Prevent this by limiting the minimum value to zero as is already
done for the left and bottom values.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2938
Cc: mesa-stable
Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12055>

diff --git a/src/gallium/drivers/lima/lima_draw.c b/src/gallium/drivers/lima/lima_draw.c
index 3d29fcc..161fc72 100644 (file)
--- a/src/gallium/drivers/lima/lima_draw.c
+++ b/src/gallium/drivers/lima/lima_draw.c
@@ -72,14 +72,14 @@ lima_clip_scissor_to_viewport(struct lima_context *ctx)
 
    viewport_left = MAX2(ctx->viewport.left, 0);
    cscissor->minx = MAX2(cscissor->minx, viewport_left);
-   viewport_right = MIN2(ctx->viewport.right, fb->base.width);
+   viewport_right = MIN2(MAX2(ctx->viewport.right, 0), fb->base.width);
    cscissor->maxx = MIN2(cscissor->maxx, viewport_right);
    if (cscissor->minx > cscissor->maxx)
       cscissor->minx = cscissor->maxx;
 
    viewport_bottom = MAX2(ctx->viewport.bottom, 0);
    cscissor->miny = MAX2(cscissor->miny, viewport_bottom);
-   viewport_top = MIN2(ctx->viewport.top, fb->base.height);
+   viewport_top = MIN2(MAX2(ctx->viewport.top, 0), fb->base.height);
    cscissor->maxy = MIN2(cscissor->maxy, viewport_top);
    if (cscissor->miny > cscissor->maxy)
       cscissor->miny = cscissor->maxy;