The link_status array was not large enough to read the Adjust Request Post Cursor2 register. Adjust the size to include it. Found with a -Warray-bounds build:

drivers/gpu/drm/drm_dp_helper.c: In function 'drm_dp_get_adjust_request_post_cursor': drivers/gpu/drm/drm_dp_helper.c:59:27: error: array subscript 10 is outside array bounds of 'const u8[6]' {aka 'const unsigned char[6]'} [-Werror=array-bounds] 59 | return link_status[r - DP_LANE0_1_STATUS]; | ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/drm_dp_helper.c:147:51: note: while referencing 'link_status' 147 | u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 79465e0ffeb9 ("drm/dp: Add helper to get post-cursor adjustments") Signed-off-by: Kees Cook keescook@chromium.org --- v2: Fix missed array size change in intel_dp_check_mst_status() --- drivers/gpu/drm/i915/display/intel_dp.c | 8 ++++---- include/drm/drm_dp_helper.h | 10 +++++++++- 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 5a8206298691..97367afc7243 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -3647,17 +3647,17 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)

for (;;) { /* - * The +2 is because DP_DPRX_ESI_LEN is 14, but we then + * The +10 is because while DP_DPRX_ESI_LEN is 14, we then * pass in "esi+10" to drm_dp_channel_eq_ok(), which - * takes a 6-byte array. So we actually need 16 bytes - * here. + * takes a DP_LINK_STATUS_SIZE array. So we actually need + * 10 bytes more than DP_LINK_STATUS_SIZE. * * Somebody who knows what the limits actually are * should check this, but for now this is at least * harmless and avoids a valid compiler warning about * using more of the array than we have allocated. */ - u8 esi[DP_DPRX_ESI_LEN+2] = {}; + u8 esi[DP_LINK_STATUS_SIZE + 10] = {}; bool handled; int retry;

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 472dac376284..277643d2fe2c 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -1517,7 +1517,15 @@ enum drm_dp_phy { #define DP_MST_LOGICAL_PORT_0 8

#define DP_LINK_CONSTANT_N_VALUE 0x8000 -#define DP_LINK_STATUS_SIZE 6 +/* + * DPCD registers in link_status: + * Link Status: 0x202 through 0x204 + * Sink Status: 0x205 + * Adjust Request: 0x206 through 0x207 + * Training Score: 0x208 through 0x20b + * AR Post Cursor2: 0x20c + */ +#define DP_LINK_STATUS_SIZE 11 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE], int lane_count); bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],