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drm/i915/dp: prevent potential div-by-zero

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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: a4a157777c ("drm/i915/dp: Compute DSC pipe config in atomic check")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230418140430.69902-1-n.zhandarovich@fintech.ru
(cherry picked from commit 51f7008239)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
This commit is contained in:
Nikita Zhandarovich 2023-04-18 07:04:30 -07:00 committed by Joonas Lahtinen
parent a41d985902
commit 0ff80028e2
1 changed files with 5 additions and 0 deletions
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5
drivers/gpu/drm/i915/display/intel_dp.c
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@ -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;