On Tue, 05 Apr 2022, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Make sure the LFP data table pointers sane. Sensible looking
> table entries, everything points correctly into the data block,
> etc.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
I can't adequately describe my opinion about the design of the data
structures here. Sheesh.
Dunno why we keep struct lvds_lfp_data_entry and struct
bdb_lvds_lfp_data around, as they don't really reflect reality.
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_bios.c | 82 ++++++++++++++++++++++-
> 1 file changed, 81 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index 000544280c35..cd82ea4de8e1 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -133,6 +133,18 @@ static u32 block_offset(const void *bdb, enum bdb_block_id section_id)
> return block - bdb;
> }
>
> +/* size of the block excluding the header */
> +static u32 block_size(const void *bdb, enum bdb_block_id section_id)
> +{
> + const void *block;
> +
> + block = find_raw_section(bdb, section_id);
> + if (!block)
> + return 0;
> +
> + return get_blocksize(block);
> +}
> +
> struct bdb_block_entry {
> struct list_head node;
> enum bdb_block_id section_id;
> @@ -191,6 +203,74 @@ static const struct {
> .min_size = sizeof(struct bdb_generic_dtd), },
> };
>
> +static bool validate_lfp_data_ptrs(const void *bdb,
> + const struct bdb_lvds_lfp_data_ptrs *ptrs)
> +{
> + int fp_timing_size, dvo_timing_size, panel_pnp_id_size;
> + int data_block_size, lfp_data_size;
> + int i;
> +
> + data_block_size = block_size(bdb, BDB_LVDS_LFP_DATA);
> + if (data_block_size == 0)
> + return false;
> +
> + /* always 3 indicating the presence of fp_timing+dvo_timing+panel_pnp_id */
> + if (ptrs->lvds_entries != 3)
> + return false;
> +
> + fp_timing_size = ptrs->ptr[0].fp_timing.table_size;
> + dvo_timing_size = ptrs->ptr[0].dvo_timing.table_size;
> + panel_pnp_id_size = ptrs->ptr[0].panel_pnp_id.table_size;
> +
> + /* fp_timing has variable size */
> + if (fp_timing_size < 32 ||
> + dvo_timing_size != sizeof(struct lvds_dvo_timing) ||
> + panel_pnp_id_size != sizeof(struct lvds_pnp_id))
> + return false;
> +
> + lfp_data_size = ptrs->ptr[1].fp_timing.offset - ptrs->ptr[0].fp_timing.offset;
> + if (16 * lfp_data_size > data_block_size)
> + return false;
> +
> + /*
> + * Except for vlv/chv machines all real VBTs seem to have 6
> + * unaccounted bytes in the fp_timing table. And it doesn't
> + * appear to be a really intentional hole as the fp_timing
> + * 0xffff terminator is always within those 6 missing bytes.
> + */
> + if (fp_timing_size + dvo_timing_size + panel_pnp_id_size != lfp_data_size &&
> + fp_timing_size + 6 + dvo_timing_size + panel_pnp_id_size != lfp_data_size)
> + return false;
> +
> + if (ptrs->ptr[0].fp_timing.offset + fp_timing_size > ptrs->ptr[0].dvo_timing.offset ||
> + ptrs->ptr[0].dvo_timing.offset + dvo_timing_size != ptrs->ptr[0].panel_pnp_id.offset ||
> + ptrs->ptr[0].panel_pnp_id.offset + panel_pnp_id_size != lfp_data_size)
> + return false;
> +
> + /* make sure the table entries have uniform size */
> + for (i = 1; i < 16; i++) {
> + if (ptrs->ptr[i].fp_timing.table_size != fp_timing_size ||
> + ptrs->ptr[i].dvo_timing.table_size != dvo_timing_size ||
> + ptrs->ptr[i].panel_pnp_id.table_size != panel_pnp_id_size)
> + return false;
> +
> + if (ptrs->ptr[i].fp_timing.offset - ptrs->ptr[i-1].fp_timing.offset != lfp_data_size ||
> + ptrs->ptr[i].dvo_timing.offset - ptrs->ptr[i-1].dvo_timing.offset != lfp_data_size ||
> + ptrs->ptr[i].panel_pnp_id.offset - ptrs->ptr[i-1].panel_pnp_id.offset != lfp_data_size)
> + return false;
> + }
> +
> + /* make sure the tables fit inside the data block */
> + for (i = 0; i < 16; i++) {
> + if (ptrs->ptr[i].fp_timing.offset + fp_timing_size > data_block_size ||
> + ptrs->ptr[i].dvo_timing.offset + dvo_timing_size > data_block_size ||
> + ptrs->ptr[i].panel_pnp_id.offset + panel_pnp_id_size > data_block_size)
> + return false;
> + }
> +
> + return true;
> +}
> +
> /* make the data table offsets relative to the data block */
> static bool fixup_lfp_data_ptrs(const void *bdb, void *ptrs_block)
> {
> @@ -211,7 +291,7 @@ static bool fixup_lfp_data_ptrs(const void *bdb, void *ptrs_block)
> ptrs->ptr[i].panel_pnp_id.offset -= offset;
> }
>
> - return true;
> + return validate_lfp_data_ptrs(bdb, ptrs);
> }
>
> static void
--
Jani Nikula, Intel Open Source Graphics Center
