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

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Message-ID: <f1d2bb84df85237f23ebf6e0f3dfecfd72d615b6.camel@perches.com>
Date: Fri, 21 Nov 2025 20:51:19 -0800
From: Joe Perches <joe@...ches.com>
To: Kees Cook <kees@...nel.org>, Vlastimil Babka <vbabka@...e.cz>
Cc: 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>, Justin
 Stitt	 <justinstitt@...gle.com>, Jann Horn <jannh@...gle.com>, Greg
 Kroah-Hartman	 <gregkh@...uxfoundation.org>, Sasha Levin
 <sashal@...nel.org>, 	linux-mm@...ck.org, 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 3/4] checkpatch: Suggest kmalloc_obj family for
 sizeof allocations

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

> +		if ($perl_version_ok &&
> +		    defined $stat &&
> +		    $stat =~ /^\+\s*($Lval)\s*\=\s*(?:$balanced_parens)?\s*((?:kv|k)[mz]alloc)\s*\(\s*($FuncArg)\s*,/) {
> +			my $oldfunc = $3;
> +			my $a1 = $4;
> +			my $newfunc = "kmalloc_obj";
> +			$newfunc = "kvmalloc_obj" if ($oldfunc eq "kvmalloc");
> +			$newfunc = "kvzalloc_obj" if ($oldfunc eq "kvzalloc");
> +			$newfunc = "kzalloc_obj" if ($oldfunc eq "kzalloc");
> +
> +			if ($a1 =~ s/^sizeof\s*\S\(?([^\)]*)\)?$/$1/) {
> +				my $cnt = statement_rawlines($stat);
> +				my $herectx = get_stat_here($linenr, $cnt, $here);
> +
> +				if (WARN("ALLOC_WITH_SIZEOF",
> +					 "Prefer $newfunc over $oldfunc with sizeof\n" . $herectx) &&
> +				    $cnt == 1 &&
> +				    $fix) {
> +					$fixed[$fixlinenr] =~ s/\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*((?:kv|k)[mz]alloc)\s*\(\s*($FuncArg)\s*,/$1 = $newfunc($a1,/;
> +				}
> +			}
> +		}
> +
> +
> +# check for (kv|k)[mz]alloc with multiplies that could be kmalloc_objs/kvmalloc_objs/kzalloc_objs/kvzalloc_objs
>  		if ($perl_version_ok &&
>  		    defined $stat &&
>  		    $stat =~ /^\+\s*($Lval)\s*\=\s*(?:$balanced_parens)?\s*((?:kv|k)[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)\s*,/) {
>  			my $oldfunc = $3;
>  			my $a1 = $4;
>  			my $a2 = $10;
> -			my $newfunc = "kmalloc_array";
> -			$newfunc = "kvmalloc_array" if ($oldfunc eq "kvmalloc");
> -			$newfunc = "kvcalloc" if ($oldfunc eq "kvzalloc");
> -			$newfunc = "kcalloc" if ($oldfunc eq "kzalloc");
> +			my $newfunc = "kmalloc_objs";
> +			$newfunc = "kvmalloc_objs" if ($oldfunc eq "kvmalloc");
> +			$newfunc = "kvzalloc_objs" if ($oldfunc eq "kvzalloc");
> +			$newfunc = "kzalloc_objs" if ($oldfunc eq "kzalloc");
>  			my $r1 = $a1;
>  			my $r2 = $a2;
>  			if ($a1 =~ /^sizeof\s*\S/) {
> @@ -7284,7 +7309,9 @@ sub process {
>  					 "Prefer $newfunc over $oldfunc with multiply\n" . $herectx) &&
>  				    $cnt == 1 &&
>  				    $fix) {
> -					$fixed[$fixlinenr] =~ s/\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*((?:kv|k)[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/$1 . ' = ' . "$newfunc(" . trim($r1) . ', ' . trim($r2)/e;
> +					my $sized = trim($r2);
> +					$sized =~ s/^sizeof\s*\S\(?([^\)]*)\)?$/$1/;
> +					$fixed[$fixlinenr] =~ s/\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*((?:kv|k)[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/$1 . ' = ' . "$newfunc(" . $sized . ', ' . trim($r1)/e;
>  				}
>  			}
>  		}