Re: [PATCH v2 2/2] slub: Add method to verify memory is not freed.

[Ben Greear]

On 07/01/2011 07:11 AM, Christoph Lameter wrote:

> > +#ifdef CONFIG_SLUB_DEBUG
> > +bool verify_mem_not_deleted(const void *x)
> > +{
> > +	struct page *page;
> > +	void *object = (void *)x;
> > +	unsigned long flags;
> > +	bool rv;
> > +
> > +	if (unlikely(ZERO_OR_NULL_PTR(x)))
> > +		return false;
> > +
> > +	local_irq_save(flags);
> > +
> > +	page = virt_to_head_page(x);
> > +	if (unlikely(!PageSlab(page))) {
> > +		/* maybe it was from stack? */
> > +		rv = true;
> > +		goto out_unlock;
> > +	}
>
> The above check is problematic for slabs that have SLAB_DESTROY_BY_RCU
> set. PageSlab(page) may be true to the next rcu interval.

I do not see the problem here.  If PageSlab(page) is true, we fall
through and do the check for on-free-list, under the slab_lock().

We only return error if it is on the free list.  Would these pages
waiting on the RCU interval show up as in the free list?

Thanks,
Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/