On Tue, Dec 28, 2021 at 09:32:55AM +0100, Jens Wiklander wrote:
commit dfd0743f1d9ea76931510ed150334d571fbab49d upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org Reviewed-by: Lars Persson larper@axis.com Reviewed-by: Sumit Garg sumit.garg@linaro.org Reported-by: Patrik Lantz patrik.lantz@axis.com [JW: backport to 5.4-stable] Signed-off-by: Jens Wiklander jens.wiklander@linaro.org
drivers/tee/tee_shm.c | 177 +++++++++++++++------------------------- include/linux/tee_drv.h | 4 +- 2 files changed, 69 insertions(+), 112 deletions(-)
All backports queue up, thanks.
greg k-h