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Message-ID: <CAHUa44G+Z9LjxqqqvKRRHrfN_6QPweF_5df2uOqtRuBfa5j3pw@mail.gmail.com>
Date: Mon, 7 Apr 2025 16:55:13 +0200
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
Cc: Sumit Garg <sumit.garg@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Apurupa Pattapu <quic_apurupa@...cinc.com>,
Kees Cook <kees@...nel.org>, "Gustavo A. R. Silva" <gustavoars@...nel.org>,
Sumit Semwal <sumit.semwal@...aro.org>, Christian König <christian.koenig@....com>,
linux-arm-msm@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 02/11] tee: add close_context to TEE driver operation
Hi Amir,
On Fri, Mar 28, 2025 at 3:48 AM Amirreza Zarrabi
<amirreza.zarrabi@....qualcomm.com> wrote:
>
> The tee_context can be used to manage TEE user resources, including
> those allocated by the driver for the TEE on behalf of the user.
> The release() callback is invoked only when all resources, such as
> tee_shm, are released and there are no references to the tee_context.
>
> When a user closes the device file, the driver should notify the
> TEE to release any resources it may hold and drop the context
> references. To achieve this, a close_context() callback is
> introduced to initiate resource release in the TEE driver when
> the device file is closed.
>
> Relocate teedev_ctx_get, teedev_ctx_put, tee_device_get, and
> tee_device_get functions to tee_drv.h to make them accessible
> outside the TEE subsystem.
>
> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
> ---
> drivers/tee/tee_core.c | 39 +++++++++++++++++++++++++++++++++++++++
> drivers/tee/tee_private.h | 6 ------
> include/linux/tee_core.h | 11 +++++++++--
> include/linux/tee_drv.h | 40 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 88 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 24edce4cdbaa..22cc7d624b0c 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -72,6 +72,20 @@ struct tee_context *teedev_open(struct tee_device *teedev)
> }
> EXPORT_SYMBOL_GPL(teedev_open);
>
> +/**
> + * teedev_ctx_get() - Increment the reference count of a context
> + *
> + * This function increases the refcount of the context, which is tied to
> + * resources shared by the same tee_device. During the unregistration process,
> + * the context may remain valid even after tee_device_unregister() has returned.
> + *
> + * Users should ensure that the context's refcount is properly decreased before
> + * calling tee_device_put(), typically within the context's release() function.
> + * Alternatively, users can call tee_device_get() and teedev_ctx_get() together
> + * and release them simultaneously (see shm_alloc_helper()).
> + *
> + * @ctx: Pointer to the context
Please move this @ctx line to before the verbose description of the function.
Cheers,
Jens
> + */
> void teedev_ctx_get(struct tee_context *ctx)
> {
> if (ctx->releasing)
> @@ -79,6 +93,7 @@ void teedev_ctx_get(struct tee_context *ctx)
>
> kref_get(&ctx->refcount);
> }
> +EXPORT_SYMBOL_GPL(teedev_ctx_get);
>
> static void teedev_ctx_release(struct kref *ref)
> {
> @@ -89,6 +104,10 @@ static void teedev_ctx_release(struct kref *ref)
> kfree(ctx);
> }
>
> +/**
> + * teedev_ctx_put() - Decrease reference count on a context
> + * @ctx: pointer to the context
> + */
> void teedev_ctx_put(struct tee_context *ctx)
> {
> if (ctx->releasing)
> @@ -96,11 +115,15 @@ void teedev_ctx_put(struct tee_context *ctx)
>
> kref_put(&ctx->refcount, teedev_ctx_release);
> }
> +EXPORT_SYMBOL_GPL(teedev_ctx_put);
>
> void teedev_close_context(struct tee_context *ctx)
> {
> struct tee_device *teedev = ctx->teedev;
>
> + if (teedev->desc->ops->close_context)
> + teedev->desc->ops->close_context(ctx);
> +
> teedev_ctx_put(ctx);
> tee_device_put(teedev);
> }
> @@ -1024,6 +1047,10 @@ int tee_device_register(struct tee_device *teedev)
> }
> EXPORT_SYMBOL_GPL(tee_device_register);
>
> +/**
> + * tee_device_put() - Decrease the user count for a tee_device
> + * @teedev: pointer to the tee_device
> + */
> void tee_device_put(struct tee_device *teedev)
> {
> mutex_lock(&teedev->mutex);
> @@ -1037,7 +1064,18 @@ void tee_device_put(struct tee_device *teedev)
> }
> mutex_unlock(&teedev->mutex);
> }
> +EXPORT_SYMBOL_GPL(tee_device_put);
>
> +/**
> + * tee_device_get() - Increment the user count for a tee_device
> + * @teedev: Pointer to the tee_device
> + *
> + * If tee_device_unregister() has been called and the final user of @teedev
> + * has already released the device, this function will fail to prevent new users
> + * from accessing the device during the unregistration process.
> + *
> + * Returns: true if @teedev remains valid, otherwise false
> + */
> bool tee_device_get(struct tee_device *teedev)
> {
> mutex_lock(&teedev->mutex);
> @@ -1049,6 +1087,7 @@ bool tee_device_get(struct tee_device *teedev)
> mutex_unlock(&teedev->mutex);
> return true;
> }
> +EXPORT_SYMBOL_GPL(tee_device_get);
>
> /**
> * tee_device_unregister() - Removes a TEE device
> diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
> index 9bc50605227c..d3f40a03de36 100644
> --- a/drivers/tee/tee_private.h
> +++ b/drivers/tee/tee_private.h
> @@ -14,12 +14,6 @@
>
> int tee_shm_get_fd(struct tee_shm *shm);
>
> -bool tee_device_get(struct tee_device *teedev);
> -void tee_device_put(struct tee_device *teedev);
> -
> -void teedev_ctx_get(struct tee_context *ctx);
> -void teedev_ctx_put(struct tee_context *ctx);
> -
> struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
> struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
> unsigned long addr, size_t length);
> diff --git a/include/linux/tee_core.h b/include/linux/tee_core.h
> index a38494d6b5f4..8a4c9e30b652 100644
> --- a/include/linux/tee_core.h
> +++ b/include/linux/tee_core.h
> @@ -65,8 +65,9 @@ struct tee_device {
> /**
> * struct tee_driver_ops - driver operations vtable
> * @get_version: returns version of driver
> - * @open: called when the device file is opened
> - * @release: release this open file
> + * @open: called for a context when the device file is opened
> + * @close_context: called when the device file is closed
> + * @release: called to release the context
> * @open_session: open a new session
> * @close_session: close a session
> * @system_session: declare session as a system session
> @@ -76,11 +77,17 @@ struct tee_device {
> * @supp_send: called for supplicant to send a response
> * @shm_register: register shared memory buffer in TEE
> * @shm_unregister: unregister shared memory buffer in TEE
> + *
> + * The context given to @open might last longer than the device file if it is
> + * tied to other resources in the TEE driver. @close_context is called when the
> + * client closes the device file, even if there are existing references to the
> + * context. The TEE driver can use @close_context to start cleaning up.
> */
> struct tee_driver_ops {
> void (*get_version)(struct tee_device *teedev,
> struct tee_ioctl_version_data *vers);
> int (*open)(struct tee_context *ctx);
> + void (*close_context)(struct tee_context *ctx);
> void (*release)(struct tee_context *ctx);
> int (*open_session)(struct tee_context *ctx,
> struct tee_ioctl_open_session_arg *arg,
> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> index a54c203000ed..ce23fd42c5d4 100644
> --- a/include/linux/tee_drv.h
> +++ b/include/linux/tee_drv.h
> @@ -96,6 +96,46 @@ struct tee_param {
> } u;
> };
>
> +/**
> + * tee_device_get() - Increment the user count for a tee_device
> + * @teedev: Pointer to the tee_device
> + *
> + * If tee_device_unregister() has been called and the final user of @teedev
> + * has already released the device, this function will fail to prevent new users
> + * from accessing the device during the unregistration process.
> + *
> + * Returns: true if @teedev remains valid, otherwise false
> + */
> +bool tee_device_get(struct tee_device *teedev);
> +
> +/**
> + * tee_device_put() - Decrease the user count for a tee_device
> + * @teedev: pointer to the tee_device
> + */
> +void tee_device_put(struct tee_device *teedev);
> +
> +/**
> + * teedev_ctx_get() - Increment the reference count of a context
> + *
> + * This function increases the refcount of the context, which is tied to
> + * resources shared by the same tee_device. During the unregistration process,
> + * the context may remain valid even after tee_device_unregister() has returned.
> + *
> + * Users should ensure that the context's refcount is properly decreased before
> + * calling tee_device_put(), typically within the context's release() function.
> + * Alternatively, users can call tee_device_get() and teedev_ctx_get() together
> + * and release them simultaneously (see shm_alloc_helper()).
> + *
> + * @ctx: Pointer to the context
> + */
> +void teedev_ctx_get(struct tee_context *ctx);
> +
> +/**
> + * teedev_ctx_put() - Decrease reference count on a context
> + * @ctx: pointer to the context
> + */
> +void teedev_ctx_put(struct tee_context *ctx);
> +
> /**
> * tee_shm_alloc_kernel_buf() - Allocate kernel shared memory for a
> * particular TEE client driver
>
> --
> 2.34.1
>
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