Re: [PATCH 2/3] devmem: check vmalloc address on kmem read/write

[KAMEZAWA Hiroyuki]

On Wed, 16 Sep 2009 09:39:41 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> 
> Otherwise vmalloc_to_page() will BUG().
> 
> This also makes the kmem read/write implementation aligned with mem(4):
> "References to nonexistent locations cause errors to be returned." Here
> we return -ENXIO (inspired by Hugh) if no bytes have been transfered
> to/from user space, otherwise return partial read/write results.
> 
seems reasonable.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

> CC: Greg Kroah-Hartman <gregkh@xxxxxxx>
> CC: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> ---
>  drivers/char/mem.c |    8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> --- linux-mm.orig/drivers/char/mem.c	2009-09-16 08:52:17.000000000 +0800
> +++ linux-mm/drivers/char/mem.c	2009-09-16 09:15:03.000000000 +0800
> @@ -443,6 +443,10 @@ static ssize_t read_kmem(struct file *fi
>  			return -ENOMEM;
>  		while (count > 0) {
>  			sz = size_inside_page(p, count);
> +			if (!is_vmalloc_or_module_addr((void *)p)) {
> +				err = -ENXIO;
> +				break;
> +			}
>  			err = vread(kbuf, (char *)p, sz);
>  			if (err)
>  				break;
> @@ -543,6 +547,10 @@ static ssize_t write_kmem(struct file * 
>  			unsigned long sz = size_inside_page(p, count);
>  			unsigned long n;
>  
> +			if (!is_vmalloc_or_module_addr((void *)p)) {
> +				err = -ENXIO;
> +				break;
> +			}
>  			n = copy_from_user(kbuf, buf, sz);
>  			if (n) {
>  				err = -EFAULT;
> 
> -- 
> 
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