linux-kernel - Re: [PATCH v5 3/4] checkpatch: Suggest kmalloc

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Message-ID: <202512031511.ACA8A5DB0@keescook>
Date: Wed, 3 Dec 2025 15:12:34 -0800
From: Kees Cook <kees@...nel.org>
To: Joe Perches <joe@...ches.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, Andy Whitcroft <apw@...onical.com>,
	Dwaipayan Ray <dwaipayanray1@...il.com>,
	Lukas Bulwahn <lukas.bulwahn@...il.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Christoph Lameter <cl@...ux.com>, Marco Elver <elver@...gle.com>,
	Vegard Nossum <vegard.nossum@...cle.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>,
	Harry Yoo <harry.yoo@...cle.com>, Bill Wendling <morbo@...gle.com>,
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	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	linux-doc@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v5 3/4] checkpatch: Suggest kmalloc_obj family for sizeof
 allocations

On Fri, Nov 21, 2025 at 08:51:19PM -0800, Joe Perches wrote:
> On Fri, 2025-11-21 at 17:42 -0800, Kees Cook wrote:
> > To support shifting away from sized allocation towards typed
> > allocations, suggest the kmalloc_obj family of macros when a sizeof() is
> > present in the argument lists.
> []
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
> > @@ -7258,17 +7258,42 @@ sub process {
> >  			    "Prefer $3(sizeof(*$1)...) over $3($4...)\n" . $herecurr);
> >  		}
> >  
> > -# check for (kv|k)[mz]alloc with multiplies that could be kmalloc_array/kvmalloc_array/kvcalloc/kcalloc
> > +# check for (kv|k)[mz]alloc that could be kmalloc_obj/kvmalloc_obj/kzalloc_obj/kvzalloc_obj
> 
> There are _way_ too many of these existing uses to suggest this change
> in existing files so please add '&& !$file' to these tests

The goal would be to also do the proposed treewide change which gets
the vast majority of them converted.

-- 
Kees Cook