Commit 0ff80028 authored by Nikita Zhandarovich's avatar Nikita Zhandarovich Committed by Joonas Lahtinen
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drm/i915/dp: prevent potential div-by-zero 



drm_dp_dsc_sink_max_slice_count() may return 0 if something goes
wrong on the part of the DSC sink and its DPCD register. This null
value may be later used as a divisor in intel_dsc_compute_params(),
which will lead to an error.
In the unlikely event that this issue occurs, fix it by testing the
return value of drm_dp_dsc_sink_max_slice_count() against zero.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: a4a15777 ("drm/i915/dp: Compute DSC pipe config in atomic check")
Signed-off-by: default avatarNikita Zhandarovich <n.zhandarovich@fintech.ru>
Reviewed-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230418140430.69902-1-n.zhandarovich@fintech.ru


(cherry picked from commit 51f70082)
Signed-off-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
parent a41d9859

drivers/gpu/drm/i915/display/intel_dp.c

+5 −0
Original line number Diff line number Diff line
@@ -1601,6 +1601,11 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp, 
		pipe_config->dsc.slice_count =

			drm_dp_dsc_sink_max_slice_count(intel_dp->dsc_dpcd,

							true);

		if (!pipe_config->dsc.slice_count) {

			drm_dbg_kms(&dev_priv->drm, "Unsupported Slice Count %d\n",

				    pipe_config->dsc.slice_count);

			return -EINVAL;

		}

	} else {

		u16 dsc_max_output_bpp = 0;

		u8 dsc_dp_slice_count;