linux-kernel - Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags

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: <20260120152245.GC1134360@nvidia.com>
Date: Tue, 20 Jan 2026 11:22:45 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	Christian Koenig <christian.koenig@....com>,
	Huang Rui <ray.huang@....com>,
	Matthew Auld <matthew.auld@...el.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Benjamin LaHaise <bcrl@...ck.org>, Gao Xiang <xiang@...nel.org>,
	Chao Yu <chao@...nel.org>, Yue Hu <zbestahu@...il.com>,
	Jeffle Xu <jefflexu@...ux.alibaba.com>,
	Sandeep Dhavale <dhavale@...gle.com>,
	Hongbo Li <lihongbo22@...wei.com>,
	Chunhai Guo <guochunhai@...o.com>, Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Muchun Song <muchun.song@...ux.dev>,
	Oscar Salvador <osalvador@...e.de>,
	David Hildenbrand <david@...nel.org>,
	Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
	Mike Marshall <hubcap@...ibond.com>,
	Martin Brandenburg <martin@...ibond.com>,
	Tony Luck <tony.luck@...el.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Dave Martin <Dave.Martin@....com>,
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>,
	Carlos Maiolino <cem@...nel.org>,
	Damien Le Moal <dlemoal@...nel.org>,
	Naohiro Aota <naohiro.aota@....com>,
	Johannes Thumshirn <jth@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	"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>, Hugh Dickins <hughd@...gle.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Zi Yan <ziy@...dia.com>, Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
	Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>,
	Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
	David Howells <dhowells@...hat.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E . Hallyn" <serge@...lyn.com>,
	Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
	linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
	linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org,
	linux-mm@...ck.org, ntfs3@...ts.linux.dev, devel@...ts.orangefs.org,
	linux-xfs@...r.kernel.org, keyrings@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t
 only

On Tue, Jan 20, 2026 at 03:10:54PM +0000, Lorenzo Stoakes wrote:
> The natural implication of what you're saying is that we can no longer use this
> from _anywhere_ because - hey - passing this by value is bad so now _everything_
> has to be re-written as:

No, I'm not saying that, I'm saying this specific case where you are
making an accessor to reach an unknown value located on the heap
should be using a pointer as both a matter of style and to simplify
life for the compiler.

> 	vma_flags_t flags_to_set = mk_vma_flags(<flags>);
> 
> 	if (vma_flags_test(&flags, &flags_to_set)) { ... }

This is quite a different situation, it is a known const at compile
time value located on the stack.

> If it was just changing this one function I'd still object as it makes it differ
> from _every other test predicate_ using vma_flags_t but maybe to humour you I'd
> change it, but surely by this argument you're essentially objecting to the whole
> series?

I only think that if you are taking a heap input that is not of known
value you should continue to pass by pointer as is generally expected
in the C style we use.

And it isn't saying anything about the overall technique in the
series, just a minor note about style.

> I am not sure about this 'idiomatic kernel style' thing either, it feels rather
> conjured. Yes you wouldn't ordinarily pass something larger than a register size
> by-value, but here the intent is for it to be inlined anyway right?

Well, exactly, we don't normally pass things larger than an interger
by value, that isn't the style, so I don't think it is such a great
thing to introduce here kind of unnecessarily.

The troubles I recently had were linked to odd things like gcov and
very old still supported versions of gcc. Also I saw a power compiler
make a very strange choice to not inline something that evaluated to a
constant.

Jason