[PATCH v2 2/2] drivers/platform/x86/amd: pmf: Check for invalid Smart PC Policies

[Mario Limonciello <superm1@kernel.org>]

From: Mario Limonciello <mario.limonciello@amd.com>

commit 376a8c2a14439 ("platform/x86/amd/pmf: Update PMF Driver for
Compatibility with new PMF-TA") added support for platforms that support
an updated TA, however it also exposed a number of platforms that although
they have support for the updated TA don't actually populate a policy
binary.

Add an explicit check that the policy binary isn't empty before
initializing the TA.

Reported-by: Christian Heusel <christian@heusel.eu>
Closes: https://lore.kernel.org/platform-driver-x86/ae644428-5bf2-4b30-81ba-0b259ed3449b@heusel.eu/
Fixes: 376a8c2a14439 ("platform/x86/amd/pmf: Update PMF Driver for Compatibility with new PMF-TA")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/platform/x86/amd/pmf/tee-if.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/platform/x86/amd/pmf/tee-if.c b/drivers/platform/x86/amd/pmf/tee-if.c
index a8bf8c61669d3..7d6404ab9f041 100644
--- a/drivers/platform/x86/amd/pmf/tee-if.c
+++ b/drivers/platform/x86/amd/pmf/tee-if.c
@@ -350,6 +350,11 @@ static int amd_pmf_start_policy_engine(struct amd_pmf_dev *dev)
 	return 0;
 }
 
+static inline bool amd_pmf_pb_valid(struct amd_pmf_dev *dev)
+{
+	return memchr_inv(dev->policy_buf, 0xff, dev->policy_sz);
+}
+
 #ifdef CONFIG_AMD_PMF_DEBUG
 static void amd_pmf_hex_dump_pb(struct amd_pmf_dev *dev)
 {
@@ -377,6 +382,11 @@ static ssize_t amd_pmf_get_pb_data(struct file *filp, const char __user *buf,
 	dev->policy_buf = new_policy_buf;
 	dev->policy_sz = length;
 
+	if (!amd_pmf_pb_valid(dev)) {
+		ret = -EINVAL;
+		goto cleanup;
+	}
+
 	amd_pmf_hex_dump_pb(dev);
 	ret = amd_pmf_start_policy_engine(dev);
 	if (ret < 0)
@@ -549,6 +559,12 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
 
 	memcpy_fromio(dev->policy_buf, dev->policy_base, dev->policy_sz);
 
+	if (!amd_pmf_pb_valid(dev)) {
+		dev_info(dev->dev, "No Smart PC policy present\n");
+		ret = -EINVAL;
+		goto err_free_policy;
+	}
+
 	amd_pmf_hex_dump_pb(dev);
 
 	dev->prev_data = kzalloc(sizeof(*dev->prev_data), GFP_KERNEL);
-- 
2.43.0