linux-kernel - Re: [PATCH v2 v3.18-rc4 1/4] drm: prime: Honour O

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Date:	Wed, 12 Nov 2014 09:41:32 -0500
From:	Rob Clark <robdclark@...il.com>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	David Airlie <airlied@...ux.ie>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"patches@...aro.org" <patches@...aro.org>,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH v2 v3.18-rc4 1/4] drm: prime: Honour O_RDWR during prime-handle-to-fd

On Wed, Nov 12, 2014 at 6:38 AM, Daniel Thompson
<daniel.thompson@...aro.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@...aro.org>

Reviewed-by: Rob Clark <robdclark@...il.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
>
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