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Thu, 28 May 2026 15:37:11 -0400 X-MC-Unique: 9RtqLVQAPB-CYuUB4EPXcg-1 X-Mimecast-MFC-AGG-ID: 9RtqLVQAPB-CYuUB4EPXcg_1779997029 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1790B195609F; Thu, 28 May 2026 19:37:08 +0000 (UTC) Received: from [10.22.65.204] (unknown [10.22.65.204]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D0A071955F22; Thu, 28 May 2026 19:37:04 +0000 (UTC) Message-ID: <305848e7-f987-494c-8244-bcf8eed6fb7d@redhat.com> Date: Thu, 28 May 2026 15:37:04 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: don't allow empty relative nodemask in mpol_relative_nodemask() To: Yury Norov , Andrew Morton , David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Farhad Alemi , Rasmus Villemoes , cgroups@vger.kernel.org References: <20260528190337.878027-1-ynorov@nvidia.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20260528190337.878027-1-ynorov@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 5/28/26 3:03 PM, Yury Norov wrote: > Reassigning nodes relative an empty user-provided nodemask is useless, > and triggers divide-by-zero in the function. > > Reported-by: Farhad Alemi > Link: https://lore.kernel.org/all/CA+0ovCgxbZkXa+OU8w3s84R3KNPNxxRfmsNR-udh+afQBbGNmw@mail.gmail.com/ > Signed-off-by: Yury Norov > --- > mm/mempolicy.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 4e4421b22b59..cd961fa1eb33 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -370,8 +370,13 @@ static inline int mpol_store_user_nodemask(const struct mempolicy *pol) > static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig, > const nodemask_t *rel) > { > + unsigned int w = nodes_weight(*rel); > nodemask_t tmp; > - nodes_fold(tmp, *orig, nodes_weight(*rel)); > + > + if (w == 0) > + return -EINVAL; > + > + nodes_fold(tmp, *orig, w); > nodes_onto(*ret, tmp, *rel); > } > mpol_relative_nodemask() is a void function, so this code should fail compilation. Right? Cheers, Longman