Subject: Re: [Patch 0/2] powerpc: avoid userspace poking to legacy ioports

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 14 Feb 2008 07:42:54 +1100

On Wed, 2008-02-13 at 18:35 +0100, Christian Krafft wrote:
> sensors_detect crashes kernel on PowerPC, as it pokes directly to memory.
> This patch adds a check_legacy_ioports to read_port and write_port.
> It will now return ENXIO, instead of oopsing.
> 
> Signed-off-by: Christian Krafft <[email-masked]>

The problem is that this prevents using /proc/ioports to access PCI
IO space, which might be useful.

I hate that sensors_detect.. or for that matter any other userland code
that pokes random ports like that. It should die.

Ben.

> Index: linux.git/drivers/char/mem.c
> ===================================================================
> --- linux.git.orig/drivers/char/mem.c
> +++ linux.git/drivers/char/mem.c
> @@ -566,8 +566,13 @@ static ssize_t read_port(struct file * f
>  	char __user *tmp = buf;
>  
>  	if (!access_ok(VERIFY_WRITE, buf, count))
> -		return -EFAULT; 
> +		return -EFAULT;
> +
>  	while (count-- > 0 && i < 65536) {
> +#ifdef CONFIG_PPC_MERGE
> +		if (check_legacy_ioport(i))
> +			return -ENXIO;
> +#endif
>  		if (__put_user(inb(i),tmp) < 0) 
>  			return -EFAULT;  
>  		i++;
> @@ -585,6 +590,7 @@ static ssize_t write_port(struct file * 
>  
>  	if (!access_ok(VERIFY_READ,buf,count))
>  		return -EFAULT;
> +
>  	while (count-- > 0 && i < 65536) {
>  		char c;
>  		if (__get_user(c, tmp)) {
> @@ -592,6 +598,10 @@ static ssize_t write_port(struct file * 
>  				break;
>  			return -EFAULT; 
>  		}
> +#ifdef CONFIG_PPC_MERGE
> +		if (check_legacy_ioport(i))
> +			return -ENXIO;
> +#endif
>  		outb(c,i);
>  		i++;
>  		tmp++;
> 
> 
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