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 <chris@chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index fba9efd09e8765e014484cd75c2b091052993adf..148d8a786c8c68fa4e906cb62f07bf5bb856235b 100644 (file)
--- 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;
        }