drm/i915: Validate BDB section before reading

Make sure that the whole BDB section is within the MMIO region prior to
accessing it contents. That we don't read outside of the secion is left
up to the individual section parsers.

Signed-off-by: Chris Wilson <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
Reviewed-by: Shobhit Kumar <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index fba9efd09e87..148d8a786c8c 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -49,13 +49,19 @@ find_section(struct bdb_header *bdb, int section_id)
 	total = bdb->bdb_size;
 
 	/* walk the sections looking for section_id */
-	while (index < total) {
+	while (index + 3 < total) {
 		current_id = *(base + index);
 		index++;
+
 		current_size = *((u16 *)(base + index));
 		index += 2;
+
+		if (index + current_size > total)
+			return NULL;
+
 		if (current_id == section_id)
 			return base + index;
+
 		index += current_size;
 	}