[PATCH] dmapools: protect page_list walk in show_pools()

[PATCH] dmapools: protect page_list walk in show_pools()

[Thomas Gleixner]

show_pools() walks the page_list of a pool w/o protection against the
list modifications in alloc/free. Take pool->lock to avoid stomping
into nirvana.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
diff --git a/mm/dmapool.c b/mm/dmapool.c
index b1f0885..3df0637 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -86,10 +86,12 @@ show_pools(struct device *dev, struct device_attribute *attr, char *buf)
 		unsigned pages = 0;
 		unsigned blocks = 0;
 
+		spin_lock_irq(&pool->lock);
 		list_for_each_entry(page, &pool->page_list, page_list) {
 			pages++;
 			blocks += page->in_use;
 		}
+		spin_unlock_irq(&pool->lock);
 
 		/* per-pool info, no real statistics yet */
 		temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",

Re: [PATCH] dmapools: protect page_list walk in show_pools()

[Matthew Wilcox]

On Tue, Jun 23, 2009 at 04:41:14PM +0200, Thomas Gleixner wrote:
> show_pools() walks the page_list of a pool w/o protection against the
> list modifications in alloc/free. Take pool->lock to avoid stomping
> into nirvana.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Looks right to me.  We're already holding pools_lock here, but pools_lock
doesn't protect against the page_list.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

I don't have a tree for dmapool work ... might as well go in through
Andrew, I suppose?

> ---
> diff --git a/mm/dmapool.c b/mm/dmapool.c
> index b1f0885..3df0637 100644
> --- a/mm/dmapool.c
> +++ b/mm/dmapool.c
> @@ -86,10 +86,12 @@ show_pools(struct device *dev, struct device_attribute *attr, char *buf)
>  		unsigned pages = 0;
>  		unsigned blocks = 0;
>  
> +		spin_lock_irq(&pool->lock);
>  		list_for_each_entry(page, &pool->page_list, page_list) {
>  			pages++;
>  			blocks += page->in_use;
>  		}
> +		spin_unlock_irq(&pool->lock);
>  
>  		/* per-pool info, no real statistics yet */
>  		temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",
> 
> 

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."