On Fri, Jun 19, 2015 at 02:52:28PM +0100, Daniel Thompson wrote:
> Currently DRM_IOCTL_PRIME_HANDLE_TO_FD rejects all flags except
> (DRM|O)_CLOEXEC making it difficult (maybe impossible) for userspace
> to mmap() the resulting dma-buf even when this is supported by the
> DRM driver.
>
> It is trivial to relax the restriction and permit read/write access.
> This is 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@xxxxxxxxxx>
> ---
> 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 7fec191b45f7..6d2cf4fb4038 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 implementation 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.
> @@ -639,14 +639,11 @@ 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;
I think we should reject DRM_RDWR if there's no mmap implementation in the
underlying dma-buf vfunc table. Or in the gem version of those. Otherwise
looks ok to me, if we first resolve the dma-buf userspace mmap coherency
issue.
-Daniel
>
> - /* 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 ff6ef62d084b..092fe3fa8ec0 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -668,6 +668,7 @@ struct drm_set_client_cap {
> __u64 value;
> };
>
> +#define DRM_RDWR O_RDWR
> #define DRM_CLOEXEC O_CLOEXEC
> struct drm_prime_handle {
> __u32 handle;
> --
> 2.4.3
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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