linux-kernel - [PATCH v2 2/2] platform/x86/amd/pmf: Fix possible out-of-bound memory accesses

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Date: Tue, 27 Feb 2024 15:55:00 +0100
From: Armin Wolf <W_Armin@....de>
To: Shyam-sundar.S-k@....com
Cc: hdegoede@...hat.com,
	ilpo.jarvinen@...ux.intel.com,
	platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] platform/x86/amd/pmf: Fix possible out-of-bound memory accesses

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@....de>
---
Changes since v1:
- check if the policy buffer also has enough room for storing the length
---
 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 b3491268b6a0..09e3c620a9c7 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 + sizeof(length))
+		return -EINVAL;
+
 	cookie = *(u32 *)(dev->policy_buf + POLICY_COOKIE_OFFSET);
 	length = *(u32 *)(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