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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90e9ee07983sm18656516d6.8.2026.09.02.06.58.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Sep 2026 06:58:50 -0700 (PDT) Date: Wed, 2 Sep 2026 09:58:48 -0400 From: Gregory Price To: Liu Jing Cc: akpm@linux-foundation.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mempolicy: fix mod-by-zero in weighted_interleave_nid Message-ID: References: <20260902090346.16429-1-liujing@cmss.chinamobile.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902090346.16429-1-liujing@cmss.chinamobile.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B21DDC000B X-Stat-Signature: d7qay1q69apweozbc9zxj37aws5hbe47 X-HE-Tag: 1788357531-46865 X-HE-Meta: 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 cAyJk4Sq SOLw/AlFCAb/t6D8AjP6MXjt9k9D6vKY15MvfktvW7UnTp6r7NJFQuzgqNWzJWxbRFL/gZ5pjK6DL1eXXjcUvGMEU9wDJk66dX9uZi6fjNm6HVwUF8L50rXm7hj83TAOYRd9X6JSkYucvWEczKemaqwX6/sRUbeeA0RHBvk2gQMHEhJimp87cxA3tgNURzpi2VnW2gGIPxcpqc3yoCA/tEz3z1HTb/AiNVeL+MRKQ1OF+pFN56LDgJSwS7/F32wT6v7sV4jE35Qvnwiyp6VRoULXp0x7+CEbOJqNdh3xwwbXHV1i7easaDsbuviJfvN9zRLBrcY6pqyO0ITO8e8vBsvAJvlBAYq6GI6lC7SplGWDnMMz4cyIWJznLvSH9xB6BFzIE8zN0HE5PRytOibT3Lfn6t6IhmQy8JJiDQ5SEoGnkqKL9Tl8HZXMSTeBEfvBPnIYyixCBiS/tO5ounRS7zeqBp47slDzEr8xx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > --- > 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 > >