From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Now that qcom_scm_shm_bridge_enable() uses the struct device passed to
it as argument to make the QCOM_SCM_MP_SHM_BRIDGE_ENABLE SCM call, we
can move the TZMem initialization before the assignment of the __scm
pointer in the SCM driver (which marks SCM as ready to users) thus
fixing the potential race between consumer calls and the memory pool
initialization.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/firmware/qcom/qcom_scm.c | 46 +++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 26 deletions(-)

diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
index 3dfc7d410348a4b17b22acee18b51949c58f7351..561d4db7a847419fe5f9f034b09554de6a16a161 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -2250,6 +2250,26 @@ static int qcom_scm_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = of_reserved_mem_device_init(scm->dev);
+	if (ret && ret != -ENODEV)
+		return dev_err_probe(scm->dev, ret,
+				     "Failed to setup the reserved memory region for TZ mem\n");
+
+	ret = qcom_tzmem_enable(scm->dev);
+	if (ret)
+		return dev_err_probe(scm->dev, ret,
+				     "Failed to enable the TrustZone memory allocator\n");
+
+	memset(&pool_config, 0, sizeof(pool_config));
+	pool_config.initial_size = 0;
+	pool_config.policy = QCOM_TZMEM_POLICY_ON_DEMAND;
+	pool_config.max_size = SZ_256K;
+
+	scm->mempool = devm_qcom_tzmem_pool_new(scm->dev, &pool_config);
+	if (IS_ERR(scm->mempool))
+		return dev_err_probe(scm->dev, PTR_ERR(scm->mempool),
+				     "Failed to create the SCM memory pool\n");
+
 	/* Paired with smp_load_acquire() in qcom_scm_is_available(). */
 	smp_store_release(&__scm, scm);
 
@@ -2283,32 +2303,6 @@ static int qcom_scm_probe(struct platform_device *pdev)
 	if (of_property_read_bool(pdev->dev.of_node, "qcom,sdi-enabled") || !download_mode)
 		qcom_scm_disable_sdi();
 
-	ret = of_reserved_mem_device_init(__scm->dev);
-	if (ret && ret != -ENODEV) {
-		dev_err_probe(__scm->dev, ret,
-			      "Failed to setup the reserved memory region for TZ mem\n");
-		goto err;
-	}
-
-	ret = qcom_tzmem_enable(__scm->dev);
-	if (ret) {
-		dev_err_probe(__scm->dev, ret,
-			      "Failed to enable the TrustZone memory allocator\n");
-		goto err;
-	}
-
-	memset(&pool_config, 0, sizeof(pool_config));
-	pool_config.initial_size = 0;
-	pool_config.policy = QCOM_TZMEM_POLICY_ON_DEMAND;
-	pool_config.max_size = SZ_256K;
-
-	__scm->mempool = devm_qcom_tzmem_pool_new(__scm->dev, &pool_config);
-	if (IS_ERR(__scm->mempool)) {
-		ret = dev_err_probe(__scm->dev, PTR_ERR(__scm->mempool),
-				    "Failed to create the SCM memory pool\n");
-		goto err;
-	}
-
 	/*
 	 * Initialize the QSEECOM interface.
 	 *

-- 
2.48.1

On 6/25/25 10:14 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> Now that qcom_scm_shm_bridge_enable() uses the struct device passed to
> it as argument to make the QCOM_SCM_MP_SHM_BRIDGE_ENABLE SCM call, we
> can move the TZMem initialization before the assignment of the __scm
> pointer in the SCM driver (which marks SCM as ready to users) thus
> fixing the potential race between consumer calls and the memory pool
> initialization.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> ---

I'm not sure any user of tzmem ever checks qcom_scm_is_available()

(or is it orthogonal to this problem?)

Konrad

On Wed, Jun 25, 2025 at 4:47 PM Konrad Dybcio
<konrad.dybcio@oss.qualcomm.com> wrote:
>
> On 6/25/25 10:14 AM, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > Now that qcom_scm_shm_bridge_enable() uses the struct device passed to
> > it as argument to make the QCOM_SCM_MP_SHM_BRIDGE_ENABLE SCM call, we
> > can move the TZMem initialization before the assignment of the __scm
> > pointer in the SCM driver (which marks SCM as ready to users) thus
> > fixing the potential race between consumer calls and the memory pool
> > initialization.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > ---
>
> I'm not sure any user of tzmem ever checks qcom_scm_is_available()
>

Well, they all should, right? At least the ICE and fastrpc drivers do
check this from a quick glance. Also: every call that has more than 4
arguments will be an implicit user of tzmem.

Bartosz

On Wed, Jun 25, 2025 at 10:14:50AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> Now that qcom_scm_shm_bridge_enable() uses the struct device passed to
> it as argument to make the QCOM_SCM_MP_SHM_BRIDGE_ENABLE SCM call, we
> can move the TZMem initialization before the assignment of the __scm
> pointer in the SCM driver (which marks SCM as ready to users) thus
> fixing the potential race between consumer calls and the memory pool
> initialization.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Good to see this being worked on.

Perhaps you can add:

Reported-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/all/20250120151000.13870-1-johan+linaro@kernel.org/

Johan