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Subject[PATCH v1 13/14] tee: use reference counting for tee_context
Date
From: Volodymyr Babchuk <vlad.babchuk@gmail.com>

We need to ensure that tee_context is present until last
shared buffer will be freed.

Signed-off-by: Volodymyr Babchuk <vlad.babchuk@gmail.com>
---
drivers/tee/tee_core.c | 40 +++++++++++++++++++++++++++++++---------
drivers/tee/tee_private.h | 3 +++
drivers/tee/tee_shm.c | 7 +++++++
include/linux/tee_drv.h | 7 +++++++
4 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 295910f..3d49ac2 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -54,6 +54,7 @@ static int tee_open(struct inode *inode, struct file *filp)
goto err;
}

+ kref_init(&ctx->refcount);
ctx->teedev = teedev;
INIT_LIST_HEAD(&ctx->list_shm);
filp->private_data = ctx;
@@ -68,19 +69,40 @@ static int tee_open(struct inode *inode, struct file *filp)
return rc;
}

-static int tee_release(struct inode *inode, struct file *filp)
+void teedev_ctx_get(struct tee_context *ctx)
{
- struct tee_context *ctx = filp->private_data;
- struct tee_device *teedev = ctx->teedev;
- struct tee_shm *shm;
+ if (ctx->releasing)
+ return;
+
+ kref_get(&ctx->refcount);
+}

+static void teedev_ctx_release(struct kref *ref)
+{
+ struct tee_context *ctx = container_of(ref, struct tee_context,
+ refcount);
+ ctx->releasing = true;
ctx->teedev->desc->ops->release(ctx);
- mutex_lock(&ctx->teedev->mutex);
- list_for_each_entry(shm, &ctx->list_shm, link)
- shm->ctx = NULL;
- mutex_unlock(&ctx->teedev->mutex);
kfree(ctx);
- tee_device_put(teedev);
+}
+
+void teedev_ctx_put(struct tee_context *ctx)
+{
+ if (ctx->releasing)
+ return;
+
+ kref_put(&ctx->refcount, teedev_ctx_release);
+}
+
+static void teedev_close_context(struct tee_context *ctx)
+{
+ tee_device_put(ctx->teedev);
+ teedev_ctx_put(ctx);
+}
+
+static int tee_release(struct inode *inode, struct file *filp)
+{
+ teedev_close_context(filp->private_data);
return 0;
}

diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
index 2bc2b5a..85d99d6 100644
--- a/drivers/tee/tee_private.h
+++ b/drivers/tee/tee_private.h
@@ -73,4 +73,7 @@ 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);
+
#endif /*TEE_PRIVATE_H*/
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 1ed708c..5176c83 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -53,6 +53,9 @@ static void tee_shm_release(struct tee_shm *shm)
kfree(shm->pages);
}

+ if (shm->ctx)
+ teedev_ctx_put(shm->ctx);
+
kfree(shm);

tee_device_put(teedev);
@@ -187,6 +190,7 @@ struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
}

if (ctx) {
+ teedev_ctx_get(ctx);
mutex_lock(&teedev->mutex);
list_add_tail(&shm->link, &ctx->list_shm);
mutex_unlock(&teedev->mutex);
@@ -256,6 +260,8 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
return ERR_PTR(-EINVAL);
}

+ teedev_ctx_get(ctx);
+
shm = kzalloc(sizeof(*shm), GFP_KERNEL);
if (!shm) {
ret = ERR_PTR(-ENOMEM);
@@ -332,6 +338,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
kfree(shm->pages);
}
kfree(shm);
+ teedev_ctx_put(ctx);
tee_device_put(teedev);
return ret;
}
diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
index d773827..6aaef65 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h
@@ -17,6 +17,7 @@

#include <linux/types.h>
#include <linux/idr.h>
+#include <linux/kref.h>
#include <linux/list.h>
#include <linux/tee.h>

@@ -42,11 +43,17 @@ struct tee_shm_pool;
* @teedev: pointer to this drivers struct tee_device
* @list_shm: List of shared memory object owned by this context
* @data: driver specific context data, managed by the driver
+ * @refcount: reference counter for this structure
+ * @releasing: flag that indicates if context is being released right now.
+ * It is needed to break circular dependency on context during
+ * shared memory release.
*/
struct tee_context {
struct tee_device *teedev;
struct list_head list_shm;
void *data;
+ struct kref refcount;
+ bool releasing;
};

struct tee_param_memref {
--
2.7.4
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