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.

Fixes: 7c45534afa44 ("platform/x86/amd/pmf: Add support for PMF Policy Binary")
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20240304205005.10078-5-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/drivers/platform/x86/amd/pmf/tee-if.c b/drivers/platform/x86/amd/pmf/tee-if.c
index 71ea7eefc211586ca619154179a21b942cf44f34..75370431a82ef407e20b4f207994438c3bb59000 100644 (file)
--- a/drivers/platform/x86/amd/pmf/tee-if.c
+++ b/drivers/platform/x86/amd/pmf/tee-if.c
@@ -249,11 +249,17 @@ static int amd_pmf_start_policy_engine(struct amd_pmf_dev *dev)
        struct cookie_header *header;
        int res;
 
+       if (dev->policy_sz < POLICY_COOKIE_OFFSET + sizeof(*header))
+               return -EINVAL;
+
        header = (struct cookie_header *)(dev->policy_buf + POLICY_COOKIE_OFFSET);
 
        if (header->sign != POLICY_SIGN_COOKIE || !header->length)
                return -EINVAL;
 
+       if (dev->policy_sz < header->length + 512)
+               return -EINVAL;
+
        /* Update the actual length */
        dev->policy_sz = header->length + 512;
        res = amd_pmf_invoke_cmd_init(dev);