linux-kernel - [RFC v2 3/6] tee: add private login method for kernel clients

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Message-Id: <1564489420-677-4-git-send-email-sumit.garg@linaro.org>
Date:   Tue, 30 Jul 2019 17:53:37 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     keyrings@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Cc:     jens.wiklander@...aro.org, corbet@....net, dhowells@...hat.com,
        jejb@...ux.ibm.com, jarkko.sakkinen@...ux.intel.com,
        zohar@...ux.ibm.com, jmorris@...ei.org, serge@...lyn.com,
        casey@...aufler-ca.com, ard.biesheuvel@...aro.org,
        daniel.thompson@...aro.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        tee-dev@...ts.linaro.org, Sumit Garg <sumit.garg@...aro.org>
Subject: [RFC v2 3/6] tee: add private login method for kernel clients

There are use-cases where user-space shouldn't be allowed to communicate
directly with a TEE device which is dedicated to provide a specific
service for a kernel client. So add a private login method for kernel
clients and disallow user-space to open-session using GP implementation
defined login method range: (0x80000000 - 0xFFFFFFFF).

Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
---
 drivers/tee/tee_core.c   | 6 ++++++
 include/uapi/linux/tee.h | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 0f16d9f..2c2f646 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -334,6 +334,12 @@ static int tee_ioctl_open_session(struct tee_context *ctx,
 			goto out;
 	}
 
+	if (arg.clnt_login & TEE_IOCTL_LOGIN_MASK) {
+		pr_debug("login method not allowed for user-space client\n");
+		rc = -EPERM;
+		goto out;
+	}
+
 	rc = ctx->teedev->desc->ops->open_session(ctx, &arg, params);
 	if (rc)
 		goto out;
diff --git a/include/uapi/linux/tee.h b/include/uapi/linux/tee.h
index 4b9eb06..a0a3d52 100644
--- a/include/uapi/linux/tee.h
+++ b/include/uapi/linux/tee.h
@@ -172,6 +172,14 @@ struct tee_ioctl_buf_data {
 #define TEE_IOCTL_LOGIN_APPLICATION		4
 #define TEE_IOCTL_LOGIN_USER_APPLICATION	5
 #define TEE_IOCTL_LOGIN_GROUP_APPLICATION	6
+/*
+ * Disallow user-space to use GP implementation specific login
+ * method range (0x80000000 - 0xFFFFFFFF). This range is rather
+ * being reserved for REE kernel clients or TEE implementation.
+ */
+#define TEE_IOCTL_LOGIN_MASK			0x80000000
+/* Private login method for REE kernel clients */
+#define TEE_IOCTL_LOGIN_REE_KERNEL		0x80000000
 
 /**
  * struct tee_ioctl_param - parameter
-- 
2.7.4