Re: [PATCH v2 v3.18-rc4 1/4] drm: prime: Honour O_RDWR during prime-handle-to-fd

Rob Clark
2014-11-12T14:41:35Z

On Wed, Nov 12, 2014 at 6:38 AM, Daniel Thompson
<daniel.thompson@linaro.org> wrote:
> Currently DRM_IOCTL_PRIME_HANDLE_TO_FD rejects all flags except
> (DRM|O)_CLOEXEC making it hard for the userspace to generate a file
> descriptor that can be used by mmap().
>
> It is easy to relax the restriction and allow read/write permissions.
> This should be safe because the flags are seldom touched by drm; mostly
> they are passed verbatim to dma_buf calls.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

Reviewed-by: Rob Clark <robdclark@gmail.com>

> ---
> drivers/gpu/drm/drm_prime.c | 9 +++------
> include/uapi/drm/drm.h | 1 +
> 2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 78ca30808422..8467b17c8053 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -331,7 +331,7 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
> * drm_gem_prime_export - helper library implemention of the export callback
> * @dev: drm_device to export from
> * @obj: GEM object to export
> - * @flags: flags like DRM_CLOEXEC
> + * @flags: flags like DRM_CLOEXEC and DRM_RDWR
> *
> * This is the implementation of the gem_prime_export functions for GEM drivers
> * using the PRIME helpers.
> @@ -635,14 +635,11 @@ int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
> return -ENOSYS;
>
> /* check flags are valid */
> - if (args->flags & ~DRM_CLOEXEC)
> + if (args->flags & ~(DRM_CLOEXEC | DRM_RDWR))
> return -EINVAL;
>
> - /* we only want to pass DRM_CLOEXEC which is == O_CLOEXEC */
> - flags = args->flags & DRM_CLOEXEC;
> -
> return dev->driver->prime_handle_to_fd(dev, file_priv,
> - args->handle, flags, &args->fd);
> + args->handle, args->flags, &args->fd);
> }
>
> int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index b0b855613641..89c2b68ddc51 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -660,6 +660,7 @@ struct drm_set_client_cap {
> __u64 value;
> };
>
> +#define DRM_RDWR O_RDWR
> #define DRM_CLOEXEC O_CLOEXEC
> struct drm_prime_handle {
> __u32 handle;
> --
> 1.9.3
>