[PATCH v2 2/6] drm/i915/bios: Add some size checks to SPI VBT read

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Unify the SPI vs. PCI ROM VBT read codepaths a bit by
pulling some size overflow checks from the PCI side
into the SPI side.

v2: s/drm_dbg()/drm_dbg_kms()/

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_bios.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index b00aad23d6c2..37f30bb76e08 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -3088,11 +3088,22 @@ static struct vbt_header *spi_oprom_get_vbt(struct intel_display *display,
 	if (count >= oprom_size)
 		goto err_not_found;
 
+	if (sizeof(struct vbt_header) > oprom_size - count) {
+		drm_dbg_kms(display->drm, "VBT header incomplete\n");
+		goto err_not_found;
+	}
+
 	/* Get VBT size and allocate space for the VBT */
 	vbt_size = intel_spi_read(&i915->uncore,
 				  found + offsetof(struct vbt_header, vbt_size));
 	vbt_size &= 0xffff;
 
+	if (vbt_size > oprom_size - count) {
+		drm_dbg_kms(display->drm,
+			    "VBT incomplete (vbt_size overflows)\n");
+		goto err_not_found;
+	}
+
 	vbt = kzalloc(round_up(vbt_size, 4), GFP_KERNEL);
 	if (!vbt)
 		goto err_not_found;
-- 
2.44.2