linux-kernel - Re: [PATCH v2] 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: <uw7ullt3ztwxiibsdffvphehi7r5g2nxqepcggilgalhv77gso@3h5uqgwodzl3>
Date: Fri, 5 Sep 2025 10:13:15 +0100
From: Kiryl Shutsemau <kirill@...temov.name>
To: Pankaj Raghav <kernel@...kajraghav.com>
Cc: Zi Yan <ziy@...dia.com>, Ryan Roberts <ryan.roberts@....com>, 
	David Hildenbrand <david@...hat.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Baolin Wang <baolin.wang@...ux.alibaba.com>, Barry Song <baohua@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Nico Pache <npache@...hat.com>, Dev Jain <dev.jain@....com>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, linux-kernel@...r.kernel.org, willy@...radead.org, 
	linux-mm@...ck.org, mcgrof@...nel.org, gost.dev@...sung.com, 
	Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH v2] huge_memory: return -EINVAL in folio split functions
 when THP is disabled

On Fri, Sep 05, 2025 at 10:13:05AM +0200, Pankaj Raghav wrote:
> On 9/4/25 17:26, Kiryl Shutsemau wrote:
> > On Thu, Sep 04, 2025 at 11:51:29AM +0200, 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. As large folios depend on CONFIG_THP, issue warning as this function
> >> should not be called without a large folio.
> >>
> >> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> > 
> > Acked-by: Kiryl Shutsemau <kas@...nel.org>
> > 
> > Just curious, did you give BUILD_BUG() a try?
> > 
> 
> Yes, I tried BUILD_BUG() but it actually fails the build because truncate_inode_partial_folio()
> calls try_folio_split().
> 
> It won't be called in runtime because there is a check for large folios before we call this
> function. So a runtime warning is better in this case.

If truncate_inode_partial_folio() shouldn't ever be calling on THP=n
kernel, it also can be BUILD_BUG(). Just saying :P

-- 
  Kiryl Shutsemau / Kirill A. Shutemov