Add a helper to get a pointer to struct displayid_header. To be
pedantic, add buffer overflow checks to not touch the base if that
itself would overflow.
Cc: Iaroslav Boliukin <iam@xxxxxxx>
Cc: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
drivers/gpu/drm/drm_displayid.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_displayid.c b/drivers/gpu/drm/drm_displayid.c
index 38ea8203df45..7d03159dc146 100644
--- a/drivers/gpu/drm/drm_displayid.c
+++ b/drivers/gpu/drm/drm_displayid.c
@@ -7,13 +7,28 @@
#include <drm/drm_edid.h>
#include <drm/drm_print.h>
+static const struct displayid_header *
+displayid_get_header(const u8 *displayid, int length, int index)
+{
+ const struct displayid_header *base;
+
+ if (sizeof(*base) > length - index)
+ return ERR_PTR(-EINVAL);
+
+ base = (const struct displayid_header *)&displayid[index];
+
+ return base;
+}
+
static int validate_displayid(const u8 *displayid, int length, int idx)
{
int i, dispid_length;
u8 csum = 0;
const struct displayid_header *base;
- base = (const struct displayid_header *)&displayid[idx];
+ base = displayid_get_header(displayid, length, idx);
+ if (IS_ERR(base))
+ return PTR_ERR(base);
DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
base->rev, base->bytes, base->prod_id, base->ext_count);
--
2.34.1
