[alsa-devel] [PATCH 3/3] ALSA: pcm: implement the ioctl/mmap filter for the anonymous dup

[Takashi Iwai]

On Tue, 29 Jan 2019 18:59:09 +0100,
Jaroslav Kysela wrote:
> 
> Create seven control bits to allow the various restrictions for the
> anonymous file descriptor.
> 
> Signed-off-by: Jaroslav Kysela <perex at perex.cz>
> ---
>  include/sound/pcm.h         |  1 +
>  include/uapi/sound/asound.h |  9 +++++
>  sound/core/pcm_native.c     | 85 ++++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 94 insertions(+), 1 deletion(-)
> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index 61e4c69e73c7..29d22a3a458c 100644
> --- a/include/sound/pcm.h
> +++ b/include/sound/pcm.h
> @@ -226,6 +226,7 @@ struct snd_pcm_ops {
>  struct snd_pcm_file {
>  	struct snd_pcm_substream *substream;
>  	int no_compat_mmap;
> +	unsigned int perm;		/* file descriptor permissions */
>  	unsigned int user_pversion;	/* supported protocol version */
>  };
>  
> diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
> index ebc17d5a3490..29d3a16caa9a 100644
> --- a/include/uapi/sound/asound.h
> +++ b/include/uapi/sound/asound.h
> @@ -571,6 +571,15 @@ enum {
>  #define SNDRV_CHMAP_PHASE_INVERSE	(0x01 << 16)
>  #define SNDRV_CHMAP_DRIVER_SPEC		(0x02 << 16)
>  
> +#define SNDRV_PCM_PERM_MMAP		(1<<0)
> +#define SNDRV_PCM_PERM_MMAP_STATUS	(1<<1)
> +#define SNDRV_PCM_PERM_MMAP_CONTROL	(1<<2)
> +#define SNDRV_PCM_PERM_RW		(1<<3)
> +#define SNDRV_PCM_PERM_CONTROL		(1<<4)
> +#define SNDRV_PCM_PERM_STATUS		(1<<5)
> +#define SNDRV_PCM_PERM_SYNC		(1<<6)
> +#define SNDRV_PCM_PERM_MAX		((SNDRV_PCM_PERM_SYNC<<1)-1)

I'd name it SNDRV_PCM_PERM_MASK, and ...

> @@ -2850,10 +2851,11 @@ static int snd_pcm_anonymous_dup(struct file *file,
>  	int flags;
>  	struct file *nfile;
>  	struct snd_pcm *pcm = substream->pcm;
> +	struct snd_pcm_file *pcm_file;
>  
>  	if (get_user(perm, (int __user *)arg))
>  		return -EFAULT;
> -	if (perm < 0)
> +	if (perm < 0 || perm > SNDRV_PCM_PERM_MAX)
>  		return -ENOSYS;

... check like
	if (perm & ~SNDRV_PCM_PER_MASK)
		return -EINVAL;


thanks,

Takashi