On Wed, Dec 15, 2021 at 10:25:01AM +0100, Jens Wiklander wrote:
Since the tee subsystem does not keep a strong reference to its idle shared memory buffers, it races with other threads that try to destroy a shared memory through a close of its dma-buf fd or by unmapping the memory.
In tee_shm_get_from_id() when a lookup in teedev->idr has been successful, it is possible that the tee_shm is in the dma-buf teardown path, but that path is blocked by the teedev mutex. Since we don't have an API to tell if the tee_shm is in the dma-buf teardown path or not we must find another way of detecting this condition.
Fix this by doing the reference counting directly on the tee_shm using a new refcount_t refcount field. dma-buf is replaced by using anon_inode_getfd() instead, this separates the life-cycle of the underlying file from the tee_shm. tee_shm_put() is updated to hold the mutex when decreasing the refcount to 0 and then remove the tee_shm from teedev->idr before releasing the mutex. This means that the tee_shm can never be found unless it has a refcount larger than 0.
Fixes: 967c9cca2cc5 ("tee: generic TEE subsystem") Cc: stable@vger.kernel.org Reviewed-by: Lars Persson larper@axis.com Reviewed-by: Sumit Garg sumit.garg@linaro.org Reported-by: Patrik Lantz patrik.lantz@axis.com Signed-off-by: Jens Wiklander jens.wiklander@linaro.org
v1->v2
- fix copyright years in drivers/tee/tee_shm.c
- update kerneldoc comment for struct tee_shm with the reference counter
Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org