On Fri, 03 Dec 2021, Kees Cook keescook@chromium.org wrote:
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
Using DP_ADJUST_REQUEST_POST_CURSOR2 has been deprecated since DP 1.3 published in 2014, and Tegra is the only user of drm_dp_get_adjust_request_post_cursor().
Instead of bumping the link status read size from 6 to 11 for all drivers I'd much rather see some other (maybe Tegra specific) solution to this.
BR, Jani.
include/drm/drm_dp_helper.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
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],