[Intel-gfx] [PATCH 9/9] drm/i915/dmc: protect against loading wrong firmware

[Srivatsa, Anusha]

>-----Original Message-----
>From: De Marchi, Lucas
>Sent: Friday, June 14, 2019 2:37 PM
>To: Srivatsa, Anusha <anusha.srivatsa at intel.com>
>Cc: intel-gfx at lists.freedesktop.org; Vivi, Rodrigo <rodrigo.vivi at intel.com>
>Subject: Re: [PATCH 9/9] drm/i915/dmc: protect against loading wrong firmware
>
>On Fri, Jun 14, 2019 at 12:44:50PM -0700, Anusha Srivatsa wrote:
>>
>>
>>>-----Original Message-----
>>>From: De Marchi, Lucas
>>>Sent: Friday, June 7, 2019 2:13 AM
>>>To: intel-gfx at lists.freedesktop.org
>>>Cc: Vivi, Rodrigo <rodrigo.vivi at intel.com>; Srivatsa, Anusha
>>><anusha.srivatsa at intel.com>; De Marchi, Lucas
>>><lucas.demarchi at intel.com>
>>>Subject: [PATCH 9/9] drm/i915/dmc: protect against loading wrong
>>>firmware
>>>
>>>In intel_package_header version 2 there's a new field in the fw_info
>>>table that must be 0, otherwise it's not the correct DMC firmware. Add
>>>a check for version 2 or later.
>>>
>>>Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
>>>---
>>> drivers/gpu/drm/i915/intel_csr.c | 14 +++++++++++---
>>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>>diff --git a/drivers/gpu/drm/i915/intel_csr.c
>>>b/drivers/gpu/drm/i915/intel_csr.c
>>>index 7608e4e2950d..864531aae1a5 100644
>>>--- a/drivers/gpu/drm/i915/intel_csr.c
>>>+++ b/drivers/gpu/drm/i915/intel_csr.c
>>>@@ -120,7 +120,10 @@ struct intel_css_header {  } __packed;
>>>
>>> struct intel_fw_info {
>>>-	u16 reserved1;
>>>+	u8 reserved1;
>>>+
>>>+	/* reserved on package_header version 1, must be 0 on version 2 */
>>>+	u8 dmc_id;
>>>
>>> 	/* Stepping (A, B, C, ..., *). * is a wildcard */
>>> 	char stepping;
>>>@@ -325,12 +328,16 @@ void intel_csr_load_program(struct
>>>drm_i915_private
>>>*dev_priv)
>>>  */
>>> static u32 find_dmc_fw_offset(const struct intel_fw_info *fw_info,
>>> 			      unsigned int num_entries,
>>>-			      const struct stepping_info *si)
>>>+			      const struct stepping_info *si,
>>>+			      u8 package_ver)
>>> {
>>> 	u32 dmc_offset = CSR_DEFAULT_FW_OFFSET;
>>> 	unsigned int i;
>>>
>>> 	for (i = 0; i < num_entries; i++) {
>>>+		if (package_ver > 1 && fw_info[i].dmc_id != 0)
>>>+			continue;
>>
>>Wont we need a message here? "Wrong DMC version, not loading v_x.0x" or
>something?.."
>
>I don't think so. It's normal to have other blobs inside the firmware that we don't
>care about. At most I could put a debug, but I don't think we really care.
>
>As long as we find one we should be fine. And if we don't, then we will complain
>loudly later in this function with a DRM_ERROR().
>dmc_offset remaining as CSR_DEFAULT_FW_OFFSET has a double meaning here:
>either we didn't find any entry or we found one that had the offset set to this
>value.

Ok. Makes sense.

Reviewed-by: Anusha Srivatsa <anusha.srivatsa at intel.com>

>Lucas De Marchi
>
>>
>>Anusha
>>> 		if (fw_info[i].substepping == '*' &&
>>> 		    si->stepping == fw_info[i].stepping) {
>>> 			dmc_offset = fw_info[i].offset;
>>>@@ -508,7 +515,8 @@ parse_csr_fw_package(struct intel_csr *csr,
>>>
>>> 	fw_info = (const struct intel_fw_info *)
>>> 		((u8 *)package_header + sizeof(*package_header));
>>>-	dmc_offset = find_dmc_fw_offset(fw_info, num_entries, si);
>>>+	dmc_offset = find_dmc_fw_offset(fw_info, num_entries, si,
>>>+					package_header->header_ver);
>>> 	if (dmc_offset == CSR_DEFAULT_FW_OFFSET) {
>>> 		DRM_ERROR("DMC firmware not supported for %c stepping\n",
>>> 			  si->stepping);
>>>--
>>>2.21.0
>>