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From: Armin Wolf <W_Armin@gmx.de>
To: Shyam-sundar.S-k@amd.com
Cc: hdegoede@redhat.com,
	ilpo.jarvinen@linux.intel.com,
	platform-driver-x86@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] platform/x86/amd/pmf: Fix possible out-of-bound memory accesses
Date: Tue, 27 Feb 2024 15:55:00 +0100
Message-Id: <20240227145500.299683-2-W_Armin@gmx.de>
In-Reply-To: <20240227145500.299683-1-W_Armin@gmx.de>
References: <20240227145500.299683-1-W_Armin@gmx.de>
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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@gmx.de>
=2D--
Changes since v1:
- check if the policy buffer also has enough room for storing the length
=2D--
 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
=2D-- 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_pm=
f_dev *dev)
 	u32 cookie, length;
 	int res;

+	if (dev->policy_sz < POLICY_COOKIE_LEN + sizeof(length))
+		return -EINVAL;
+
 	cookie =3D *(u32 *)(dev->policy_buf + POLICY_COOKIE_OFFSET);
 	length =3D *(u32 *)(dev->policy_buf + POLICY_COOKIE_LEN);

 	if (cookie !=3D POLICY_SIGN_COOKIE || !length)
 		return -EINVAL;

+	if (dev->policy_sz < length + 512)
+		return -EINVAL;
+
 	/* Update the actual length */
 	dev->policy_sz =3D length + 512;
 	res =3D amd_pmf_invoke_cmd_init(dev);
=2D-
2.39.2