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

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

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.

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
> 

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