linux-kernel - Re: [PATCH] huge_memory: return -EINVAL in folio split functions when THP is disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cdbc4c22-7a6f-4c01-8d2b-550b643318d8@pankajraghav.com>
Date: Tue, 2 Sep 2025 10:59:52 +0200
From: Pankaj Raghav <kernel@...kajraghav.com>
To: David Hildenbrand <david@...hat.com>, Ryan Roberts
 <ryan.roberts@....com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 Nico Pache <npache@...hat.com>, Zi Yan <ziy@...dia.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, willy@...radead.org,
 mcgrof@...nel.org, gost.dev@...sung.com, Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH] huge_memory: return -EINVAL in folio split functions when
 THP is disabled

On 9/2/25 10:43, David Hildenbrand wrote:
> On 02.09.25 10:40, Pankaj Raghav (Samsung) wrote:
>> From: Pankaj Raghav <p.raghav@...sung.com>
>>
>> split_huge_page_to_list_[to_order](), split_huge_page() and
>> try_folio_split() return 0 on success and error codes on failure.
>>
>> When THP is disabled, these functions return 0 indicating success even
>> though an error code should be returned as it is not possible to split a
>> folio when THP is disabled.
>>
>> Make all these functions return -EINVAL to indicate failure instead of
>> 0.
>>
>> This issue was discovered while experimenting enabling large folios
>> without THP and found that returning 0 in these functions is resulting in
>> undefined behavior in truncate operations. This change fixes the issue.
> 
> Currently large folios that could be split are impossible without THP, so why should this be a fix?
> 
I was debating with myself whether it will classify as a fix or not. I have had people tell me that
I should mention it as fix even though I didn't feel like it ;)

But I agree with you, we can't hit this issue in the upstream kernel. I can remove the fixes tag in
the next version.

--
Pankaj