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@xxxxxxxxxxxxxxx
> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Lars Persson <larper@xxxxxxxx>
> Reviewed-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> Reported-by: Patrik Lantz <patrik.lantz@xxxxxxxx>
> [JW: backport to 5.4-stable]
> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> ---
> 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
