linux-kernel - Re: [PATCH v5 2/4] slab: Introduce kmalloc

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 for Android: free password hash cracker in your pocket

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

Message-ID: <CAHk-=wikqnc16e7yUTJuqnc5f4rL+y_-JpRzCLRu9WPnt3nmiQ@mail.gmail.com>
Date: Mon, 24 Nov 2025 13:35:12 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Kees Cook <kees@...nel.org>
Cc: Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, 
	David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Hyeonggon Yoo <42.hyeyoo@...il.com>, "Gustavo A . R . Silva" <gustavoars@...nel.org>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, Jann Horn <jannh@...gle.com>, 
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, Marco Elver <elver@...gle.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org, 
	Randy Dunlap <rdunlap@...radead.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Matthew Wilcox <willy@...radead.org>, Vegard Nossum <vegard.nossum@...cle.com>, 
	Harry Yoo <harry.yoo@...cle.com>, Nathan Chancellor <nathan@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
	Jonathan Corbet <corbet@....net>, Jakub Kicinski <kuba@...nel.org>, Yafang Shao <laoar.shao@...il.com>, 
	Tony Ambardar <tony.ambardar@...il.com>, Alexander Lobakin <aleksander.lobakin@...el.com>, 
	Jan Hendrik Farr <kernel@...rr.cc>, Alexander Potapenko <glider@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, linux-doc@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: Re: [PATCH v5 2/4] slab: Introduce kmalloc_obj() and family

On Mon, 24 Nov 2025 at 12:39, Kees Cook <kees@...nel.org> wrote:
>
> I'm not sure what you mean by "limit to pre-defined size". There's no
> such design in those helpers, except from the perspective of "detect
> and refuse to truncate overflows into too-small storage". Is that what
> you meant?

I meant that odd combination of checking both for minimal size and
then assigning to it, but upon re-reading it, I realize that the
"check for minimal size" was actually checking the size of the result
variable.

Those macros are illegible. And 99% of all users DO NOT WANT ANY OF
THAT COMPLEXITY.

Yes, the wrapper macros then pass in NULL, which then - using yet more
complexity - turns into a dummy thing.

Basically, if *I* find those macros unreadable - and I'm actually
fairly good at parsing those things - then they are way too
complicated.

And they aren't even complicated for a good reason. My alternate ones
did *more*, and did it with less code and less confusion.

And you added the complication to make the users less legible.

So no. We're not doing *any* of that. You make it simple and targeted
to the *common* case, of you don't do this at all. Because that
over-designed mess that actually turned some users *less* readable,
but one line shorter, was bad.

                    Linus