On Thu, 26 Mar 2020 at 14:05, Jérôme Forissier jerome@forissier.org wrote:
On Thu, Mar 26, 2020 at 8:24 AM Sumit Garg sumit.garg@linaro.org wrote:
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
OK
and disallow user-space to open-session using GP implementation defined login method range: (0x80000000 - 0xFFFFFFFF).
I'm not sure this is correct, because it would prevent the client library or the TEE supplicant from using such values, although they are part of the TEE implementation; and further, nothing mandates that an implementation-defined method should not be used directly by client applications.
Initial implementation of this patch only put restriction for single implementation-defined login method (TEE_IOCTL_LOGIN_REE_KERNEL) only. But after discussion with Jens here [1], I have changed that to restrict complete implementation-defined range. If we think to further partition this range considering API stability then I am open to that too.
[1] https://lore.kernel.org/patchwork/patch/1088062/
-Sumit
-- Jerome
Signed-off-by: Sumit Garg sumit.garg@linaro.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 37d22e3..533e7a8 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 6596f3a..19172a2 100644 --- a/include/uapi/linux/tee.h +++ b/include/uapi/linux/tee.h @@ -173,6 +173,14 @@ 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
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