Re: [PATCH] mempolicy: fix div-by-zero in alloc_pages_bulk_weighted_interleave

[Gregory Price <gourry@gourry.net>]

On Wed, Sep 02, 2026 at 05:04:12PM +0800, Liu Jing wrote:
> In alloc_pages_bulk_weighted_interleave(), if the iw_table contains
> all-zero weights for every node in the policy nodemask, weight_total
> sums to zero. The subsequent "rem_pages / weight_total" and
> "rem_pages % weight_total" trigger a divide-by-zero panic.
> 

weights can't be zero and we just fixed the rebind race

> The function already guards against !nnodes but not against a zero
> weight_total. Add the missing check, freeing the locally allocated
> weights buffer before returning.
> 
> Signed-off-by: Liu Jing <liujing@cmss.chinamobile.com>
> ---
>  mm/mempolicy.c | 5 +++++
>  1 file changed, 5 insertion(+), 0 deletion(-)
> 
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2697,6 +2697,11 @@
>  	/* calculate total, detect system default usage */
>  	for_each_node_mask(node, nodes)
>  		weight_total += weights[node];
> +
> +	if (!weight_total) {
> +		kfree(weights);
> +		return total_allocated;
> +	}
>  
>  	/*
>  	 * Calculate rounds/partial rounds to minimize __alloc_pages_bulk calls.
> 
> --
> 2.43.0
> 
>