linux-kernel - Re: [PATCH 11/20] amifb: get rid of pointless access

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Message-ID: <6f89732b-fba9-a947-6c61-5d1680747f3b@samsung.com>
Date:   Thu, 14 May 2020 15:45:09 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 11/20] amifb: get rid of pointless access_ok() calls


Hi Al,

On 5/10/20 1:45 AM, Al Viro wrote:
> From: Al Viro <viro@...iv.linux.org.uk>
> 
> addresses passed only to get_user() and put_user()

This driver lacks checks for {get,put}_user() return values so it will
now return 0 ("success") even if {get,put}_user() fails.

Am I missing something?

> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> ---
>  drivers/video/fbdev/amifb.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/video/fbdev/amifb.c b/drivers/video/fbdev/amifb.c
> index 20e03e00b66d..6062104f3afb 100644
> --- a/drivers/video/fbdev/amifb.c
> +++ b/drivers/video/fbdev/amifb.c
> @@ -1855,8 +1855,6 @@ static int ami_get_var_cursorinfo(struct fb_var_cursorinfo *var,
>  	var->yspot = par->crsr.spot_y;
>  	if (size > var->height * var->width)
>  		return -ENAMETOOLONG;
> -	if (!access_ok(data, size))
> -		return -EFAULT;
>  	delta = 1 << par->crsr.fmode;
>  	lspr = lofsprite + (delta << 1);
>  	if (par->bplcon0 & BPC0_LACE)
> @@ -1935,8 +1933,6 @@ static int ami_set_var_cursorinfo(struct fb_var_cursorinfo *var,
>  		return -EINVAL;
>  	if (!var->height)
>  		return -EINVAL;
> -	if (!access_ok(data, var->width * var->height))
> -		return -EFAULT;
>  	delta = 1 << fmode;
>  	lofsprite = shfsprite = (u_short *)spritememory;
>  	lspr = lofsprite + (delta << 1);
> 
 
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics