Re: 2.6.17-rc5-mm1

[Andy Whitcroft <apw@shadowen.org>]

Christoph Lameter wrote:
> Sigh the patch that I sent earlier will make swapon fail when adding more 
> entries if 32 entries have been defined before even if some of these are 
> later freed. Plus maybe we better leave the probing intact for arches that 
> support less than 32 swap devices and also return -EPERM like before. I 
> guess we need this one instead:
> 
> 
> Do proper boundary checking in sys_swapon().
> 
> sys_swapon currently does not limit the number of swap devices. It may as
> a result overwrite memory following the swap_info array and get into 
> entanglements with page migration since it may usethe swap types reserved 
> for page migration.
> 
> Fix this by limiting the number of swap devices in swapon to 
> MAX_SWAPFILES
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> Index: linux-2.6.17-rc5-mm2/mm/swapfile.c
> ===================================================================
> --- linux-2.6.17-rc5-mm2.orig/mm/swapfile.c	2006-06-01 10:03:07.127259731 -0700
> +++ linux-2.6.17-rc5-mm2/mm/swapfile.c	2006-06-05 13:40:45.887291175 -0700
> @@ -1408,8 +1408,13 @@ asmlinkage long sys_swapon(const char __
>  		spin_unlock(&swap_lock);
>  		goto out;
>  	}
> -	if (type >= nr_swapfiles)
> +	if (type >= nr_swapfiles) {
> +		if (nr_swapfiles >= MAX_SWAPFILES) {
> +			spin_unlock(&swap_lock);
> +			goto out;
> +		}
>  		nr_swapfiles = type+1;
> +	}
>  	INIT_LIST_HEAD(&p->extent_list);
>  	p->flags = SWP_USED;
>  	p->swap_file = NULL;

I'll shove this one onto the machine causing all the trouble.

-apw