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    Subject[PATCH 5.18 272/879] drm/edid: fix invalid EDID extension block filtering
    Date
    From: Jani Nikula <jani.nikula@intel.com>

    [ Upstream commit 3aefc722ff52076407203b6af9713de567993adf ]

    The invalid EDID block filtering uses the number of valid EDID
    extensions instead of all EDID extensions for looping the extensions in
    the copy. This is fine, by coincidence, if all the invalid blocks are at
    the end of the EDID. However, it's completely broken if there are
    invalid extensions in the middle; the invalid blocks are included and
    valid blocks are excluded.

    Fix it by modifying the base block after, not before, the copy.

    Fixes: 14544d0937bf ("drm/edid: Only print the bad edid when aborting")
    Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Signed-off-by: Jani Nikula <jani.nikula@intel.com>
    Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20220330170426.349248-1-jani.nikula@intel.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/drm_edid.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
    index cc7bd58369df..c5b86414873e 100644
    --- a/drivers/gpu/drm/drm_edid.c
    +++ b/drivers/gpu/drm/drm_edid.c
    @@ -2031,9 +2031,6 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,

    connector_bad_edid(connector, edid, edid[0x7e] + 1);

    - edid[EDID_LENGTH-1] += edid[0x7e] - valid_extensions;
    - edid[0x7e] = valid_extensions;
    -
    new = kmalloc_array(valid_extensions + 1, EDID_LENGTH,
    GFP_KERNEL);
    if (!new)
    @@ -2050,6 +2047,9 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
    base += EDID_LENGTH;
    }

    + new[EDID_LENGTH - 1] += new[0x7e] - valid_extensions;
    + new[0x7e] = valid_extensions;
    +
    kfree(edid);
    edid = new;
    }
    --
    2.35.1


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