linux-kernel - Re: [PATCH] selftests/mm: fix division-by-zero in uffd-unit-tests

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Message-ID: <e0be6864-4260-4843-a432-d47437b5d43f@kernel.org>
Date: Thu, 13 Nov 2025 10:06:42 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Carlos Llamas <cmllamas@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Peter Xu <peterx@...hat.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Shuah Khan <shuah@...nel.org>, Ujwal Kundur <ujwal.kundur@...il.com>,
 Brendan Jackman <jackmanb@...gle.com>
Cc: kernel-team@...roid.com, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org,
 "open list:MEMORY MANAGEMENT - USERFAULTFD" <linux-mm@...ck.org>,
 "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH] selftests/mm: fix division-by-zero in uffd-unit-tests

On 13.11.25 04:46, Carlos Llamas wrote:
> Commit 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global
> vars into struct") moved some of the operations previously implemented
> in uffd_setup_environment() earlier in the main test loop.
> 
> The calculation of nr_pages, which involves a division by page_size, now
> occurs before checking that default_huge_page_size() returns a non-zero
> This leads to a division-by-zero error on systems with !CONFIG_HUGETLB.
> 
> Fix this by relocating the non-zero page_size check before the nr_pages
> calculation, as it was originally implemented.
> 
> Cc: stable@...r.kernel.org

Do we CC stable on unit tests? From my recollection, no.

> Fixes: 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global vars into struct")
> Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
> ---

Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

-- 
Cheers

David