[PATCH 2/2] platform/x86/amd/pmf: Fix possible out-of-bound memory accesses

[Armin Wolf]

The length of the policy buffer is not validated before accessing it,
which means that multiple out-of-bounds memory accesses can occur.

This is especially bad since userspace can load policy binaries over
debugfs.

Compile-tested only.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
 drivers/platform/x86/amd/pmf/tee-if.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/platform/x86/amd/pmf/tee-if.c b/drivers/platform/x86/amd/pmf/tee-if.c
index 70d09103ab18..f2f9204b3a11 100644
--- a/drivers/platform/x86/amd/pmf/tee-if.c
+++ b/drivers/platform/x86/amd/pmf/tee-if.c
@@ -249,12 +249,18 @@ static int amd_pmf_start_policy_engine(struct amd_pmf_dev *dev)
 	u32 cookie, length;
 	int res;

+	if (dev->policy_sz < POLICY_COOKIE_LEN)
+		return -EINVAL;
+
 	cookie = dev->policy_buf[POLICY_COOKIE_OFFSET];
 	length = dev->policy_buf[POLICY_COOKIE_LEN];

 	if (cookie != POLICY_SIGN_COOKIE || !length)
 		return -EINVAL;

+	if (dev->policy_sz < length + 512)
+		return -EINVAL;
+
 	/* Update the actual length */
 	dev->policy_sz = length + 512;
 	res = amd_pmf_invoke_cmd_init(dev);
--
2.39.2