Re: [PATCH V2 06/11] remoteproc: qcom_q6v5_mss: Use a carveout to authenticate modem headers

[Sibi Sankar <quic_sibis@quicinc.com>]

Hey Mani,

On 1/9/23 14:02, Manivannan Sadhasivam wrote:
> On Mon, Jan 09, 2023 at 09:18:38AM +0530, Sibi Sankar wrote:
>> Any access to the dynamically allocated metadata region by the application
>> processor after assigning it to the remote Q6 will result in a XPU
>> violation. Fix this by replacing the dynamically allocated memory region
>> with a no-map carveout and unmap the modem metadata memory region before
>> passing control to the remote Q6.
>>
>> Reported-and-tested-by: Amit Pundir <amit.pundir@linaro.org>
>> Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for mem ownership switch")
>> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
>> ---
>>
>> v2:
>>   * Revert no_kernel_mapping [Mani/Robin]
>>
>>   drivers/remoteproc/qcom_q6v5_mss.c | 48 ++++++++++++++++++++++++++----
>>   1 file changed, 42 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
>> index e2f765f87ec9..b7a158751cef 100644
>> --- a/drivers/remoteproc/qcom_q6v5_mss.c
>> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
>> @@ -215,6 +215,7 @@ struct q6v5 {
>>   	size_t mba_size;
>>   	size_t dp_size;
>>   
>> +	phys_addr_t mdata_phys;
>>   	phys_addr_t mpss_phys;
>>   	phys_addr_t mpss_reloc;
>>   	size_t mpss_size;
>> @@ -973,15 +974,29 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
>>   	if (IS_ERR(metadata))
>>   		return PTR_ERR(metadata);
>>   
>> -	ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
>> -	if (!ptr) {
>> -		kfree(metadata);
>> -		dev_err(qproc->dev, "failed to allocate mdt buffer\n");
>> -		return -ENOMEM;
>> +	if (qproc->mdata_phys) {
>> +		phys = qproc->mdata_phys;
>> +		ptr = memremap(qproc->mdata_phys, size, MEMREMAP_WC);
>> +		if (!ptr) {
>> +			dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n",
>> +				&qproc->mdata_phys, size);
>> +			ret = -EBUSY;
>> +			goto free_dma_attrs;
> 
> There is no memory to free at this point.

we would just free the metadata in the no-map carveout scenario since
mdata_phys wouldn't be NULL. I can do a kfree(metadata) directly from
this branch and return as well if you think it makes things more
readable.

> 
> Thanks,
> Mani
> 
>> +		}
>> +	} else {
>> +		ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
>> +		if (!ptr) {
>> +			kfree(metadata);
>> +			dev_err(qproc->dev, "failed to allocate mdt buffer\n");
>> +			return -ENOMEM;
>> +		}
>>   	}
>>   
>>   	memcpy(ptr, metadata, size);
>>   
>> +	if (qproc->mdata_phys)
>> +		memunmap(ptr);
>> +
>>   	/* Hypervisor mapping to access metadata by modem */
>>   	mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
>>   	ret = q6v5_xfer_mem_ownership(qproc, &mdata_perm, false, true,
>> @@ -1010,7 +1025,8 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
>>   			 "mdt buffer not reclaimed system may become unstable\n");
>>   
>>   free_dma_attrs:
>> -	dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
>> +	if (!qproc->mdata_phys)
>> +		dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
>>   	kfree(metadata);
>>   
>>   	return ret < 0 ? ret : 0;
>> @@ -1893,6 +1909,26 @@ static int q6v5_alloc_memory_region(struct q6v5 *qproc)
>>   	qproc->mpss_phys = qproc->mpss_reloc = r.start;
>>   	qproc->mpss_size = resource_size(&r);
>>   
>> +	if (!child) {
>> +		node = of_parse_phandle(qproc->dev->of_node, "memory-region", 2);
>> +	} else {
>> +		child = of_get_child_by_name(qproc->dev->of_node, "metadata");
>> +		node = of_parse_phandle(child, "memory-region", 0);
>> +		of_node_put(child);
>> +	}
>> +
>> +	if (!node)
>> +		return 0;
>> +
>> +	ret = of_address_to_resource(node, 0, &r);
>> +	of_node_put(node);
>> +	if (ret) {
>> +		dev_err(qproc->dev, "unable to resolve metadata region\n");
>> +		return ret;
>> +	}
>> +
>> +	qproc->mdata_phys = r.start;
>> +
>>   	return 0;
>>   }
>>   
>> -- 
>> 2.17.1
>>
>