From: Jani Nikula <jani.nikula@xxxxxxxxx> [ Upstream commit 5bacecc3c56131c31f18b23d366f2184328fd9cf ] 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> Tested-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/4a03b3a5132642d3cdb6d4c2641422955a917292.1676580180.git.jani.nikula@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 38ea8203df45b..7d03159dc1461 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); -- 2.39.2
