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

[Manivannan Sadhasivam]

On Mon, Jan 09, 2023 at 03:35:31PM +0530, Sibi Sankar wrote:
> 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@xxxxxxxxxx>
> > > Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for mem ownership switch")
> > > Signed-off-by: Sibi Sankar <quic_sibis@xxxxxxxxxxx>
> > > ---
> > > 
> > > 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.
> 

Oops, I missed that. But yeah it is confusing too with the current way of
freeing metadata. I'd suggest using a separate label instead.

Thanks,
Mani

> > 
> > 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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