On Fri, Dec 03, 2021 at 01:25:17AM -0800, Kees Cook 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@xxxxxxxxxxxx>
> ---
> 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(-)
This sounds very familiar and I vaguely recall typing up a patch like
that a long time ago. But I obviously failed because that never seems
to have made it upstream.
Or perhaps I'm misremembering and was thinking about this instead:
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/338590/
Bonus points for adding that comment with background information on why
we need this.
Reviewed-by: Thierry Reding <treding@xxxxxxxxxx>
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