Re: [Patch v2] mm: slab: Verify the nodeid passed to ____cache_alloc_node

[Rafael Aquini <aquini@redhat.com>]

On Tue, Apr 23, 2013 at 10:31:36AM -0400, Aaron Tomlin wrote:
> Hi,
> 
> This patch is in response to BZ#42967 [1]. 
> Using VM_BUG_ON so it's used only when CONFIG_DEBUG_VM is set,
> given that ____cache_alloc_node() is a hot code path.
> 
This seems to be a valid condition to BUG_ON, though.

> Cheers,
> Aaron
> 
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=42967
> 
> ---8<---
> mm: slab: Verify the nodeid passed to ____cache_alloc_node
>     
> If the nodeid is > num_online_nodes() this can cause an
> Oops and a panic(). The purpose of this patch is to assert
> if this condition is true to aid debugging efforts rather
> than some random NULL pointer dereference or page fault.
>     
> Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
> Reviewed-by: Rik van Riel <riel@redhat.com>
>

Acked-by: Rafael Aquini <aquini@redhat.com>


 
> 
>  slab.c |    1 +
>  1 file changed, 1 insertion(+)
>  
> diff --git a/mm/slab.c b/mm/slab.c
> index e7667a3..735e8bd 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
>  -3412,6 +3412,7 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
>  	void *obj;
>  	int x;
>  
> +	VM_BUG_ON(nodeid > num_online_nodes());
>  	l3 = cachep->nodelists[nodeid];
>  	BUG_ON(!l3);