* [PATCH] mempolicy: fix mod-by-zero in weighted_interleave_nid
@ 2026-09-02 9:03 Liu Jing
2026-09-02 13:58 ` Gregory Price
0 siblings, 1 reply; 2+ messages in thread
From: Liu Jing @ 2026-09-02 9:03 UTC (permalink / raw)
To: akpm
Cc: david, ziy, matthew.brost, joshua.hahnjy, rakie.kim, byungchul,
gourry, ying.huang, apopple, linux-mm, linux-kernel, Liu Jing
In weighted_interleave_nid(), if the iw_table contains all-zero
weights for every node in the policy nodemask, weight_total sums to
zero. The subsequent "ilx % weight_total" triggers a divide-by-zero
panic.
Add a zero check returning the current NUMA node id when the total
weight is zero, consistent with the existing !nr_nodes guard.
Signed-off-by: Liu Jing <liujing@cmss.chinamobile.com>
---
mm/mempolicy.c | 4 ++++
1 file changed, 4 insertion(+), 0 deletion(-)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2218,6 +2218,10 @@
/* calculate the total weight */
for_each_node_mask(nid, nodemask)
weight_total += table ? table[nid] : 1;
+
+
+ if (!weight_total)
+ return numa_node_id();
/* Calculate the node offset based on totals */
target = ilx % weight_total;
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] mempolicy: fix mod-by-zero in weighted_interleave_nid
2026-09-02 9:03 [PATCH] mempolicy: fix mod-by-zero in weighted_interleave_nid Liu Jing
@ 2026-09-02 13:58 ` Gregory Price
0 siblings, 0 replies; 2+ messages in thread
From: Gregory Price @ 2026-09-02 13:58 UTC (permalink / raw)
To: Liu Jing
Cc: akpm, david, ziy, matthew.brost, joshua.hahnjy, rakie.kim,
byungchul, ying.huang, apopple, linux-mm, linux-kernel
On Wed, Sep 02, 2026 at 05:03:46PM +0800, Liu Jing wrote:
> In weighted_interleave_nid(), if the iw_table contains all-zero
> weights for every node in the policy nodemask, weight_total sums to
> zero. The subsequent "ilx % weight_total" triggers a divide-by-zero
> panic.
>
weights can't be zero and we just fixed the rebind race
if you're actually seeing this then there's a different bug to fix
> Add a zero check returning the current NUMA node id when the total
> weight is zero, consistent with the existing !nr_nodes guard.
>
> Signed-off-by: Liu Jing <liujing@cmss.chinamobile.com>
> ---
> mm/mempolicy.c | 4 ++++
> 1 file changed, 4 insertion(+), 0 deletion(-)
>
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2218,6 +2218,10 @@
> /* calculate the total weight */
> for_each_node_mask(nid, nodemask)
> weight_total += table ? table[nid] : 1;
> +
> +
> + if (!weight_total)
> + return numa_node_id();
>
> /* Calculate the node offset based on totals */
> target = ilx % weight_total;
>
> --
> 2.43.0
>
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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