drm/i915/gvt/fb_decoder: Fix out-of-bounds read

In case function skl_format_to_drm returns -EINVAL, fmt turns into a huge
number as fmt is of type u32, hence there is an out-of-bounds read when
using fmt as an index for array skl_pixel_formats at line 225:
plane->bpp = skl_pixel_formats[fmt].bpp;

Fix this by comparing the value returned by function skl_format_to_drm
against the size of array skl_pixel_formats, so in case it is greater than
or equal to the number of items contained in skl_pixel_formats, print an
error message and return -EINVAL.

Addresses-Coverity-ID: 1462495
Addresses-Coverity-ID: 1462502 ("Out-of-bounds read")
Fixes: 9f31d106 ("drm/i915/gvt: Add framebuffer decoder support")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/fb_decoder.c

@@ -222,6 +222,12 @@ int intel_vgpu_decode_primary_plane(struct intel_vgpu *vgpu,
 			val & PLANE_CTL_ORDER_RGBX,
 			val & PLANE_CTL_ALPHA_MASK,
 			val & PLANE_CTL_YUV422_ORDER_MASK);
+
+		if (fmt >= ARRAY_SIZE(skl_pixel_formats)) {
+			gvt_vgpu_err("Out-of-bounds pixel format index\n");
+			return -EINVAL;
+		}
+
 		plane->bpp = skl_pixel_formats[fmt].bpp;
 		plane->drm_format = skl_pixel_formats[fmt].drm_format;
 	} else {