linux-kernel - Re: [PATCH v2] drm: return -EFAULT if copy_to

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Date:   Tue, 18 Jun 2019 13:16:29 -0400
From:   Sean Paul <sean@...rly.run>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] drm: return -EFAULT if copy_to_user() fails

On Tue, Jun 18, 2019 at 04:18:43PM +0300, Dan Carpenter wrote:
> The copy_from_user() function returns the number of bytes remaining
> to be copied but we want to return a negative error code.  Otherwise
> the callers treat it as a successful copy.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Thanks Dan, I've applied this to drm-misc-fixes.

Sean

> ---
> v2: The first version was missing a chunk
> 
>  drivers/gpu/drm/drm_bufs.c  | 5 ++++-
>  drivers/gpu/drm/drm_ioc32.c | 5 ++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c
> index 68dacf8422c6..8ce9d73fab4f 100644
> --- a/drivers/gpu/drm/drm_bufs.c
> +++ b/drivers/gpu/drm/drm_bufs.c
> @@ -1351,7 +1351,10 @@ static int copy_one_buf(void *data, int count, struct drm_buf_entry *from)
>  				 .size = from->buf_size,
>  				 .low_mark = from->low_mark,
>  				 .high_mark = from->high_mark};
> -	return copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags));
> +
> +	if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags)))
> +		return -EFAULT;
> +	return 0;
>  }
>  
>  int drm_legacy_infobufs(struct drm_device *dev, void *data,
> diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
> index 586aa28024c5..a16b6dc2fa47 100644
> --- a/drivers/gpu/drm/drm_ioc32.c
> +++ b/drivers/gpu/drm/drm_ioc32.c
> @@ -378,7 +378,10 @@ static int copy_one_buf32(void *data, int count, struct drm_buf_entry *from)
>  			      .size = from->buf_size,
>  			      .low_mark = from->low_mark,
>  			      .high_mark = from->high_mark};
> -	return copy_to_user(to + count, &v, offsetof(drm_buf_desc32_t, flags));
> +
> +	if (copy_to_user(to + count, &v, offsetof(drm_buf_desc32_t, flags)))
> +		return -EFAULT;
> +	return 0;
>  }
>  
>  static int drm_legacy_infobufs32(struct drm_device *dev, void *data,
> -- 
> 2.20.1
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS