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

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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.


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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