linux-kernel - Re: [PATCH v4 2/2] slab: Introduce kmalloc

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Message-ID: <202503151137.CA3D422F3@keescook>
Date: Sat, 15 Mar 2025 11:39:08 -0700
From: Kees Cook <kees@...nel.org>
To: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
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>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org,
	Miguel Ojeda <ojeda@...nel.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 v4 2/2] slab: Introduce kmalloc_obj() and family

On Sat, Mar 15, 2025 at 03:48:30PM +1030, Gustavo A. R. Silva wrote:
> 
> > These each return the assigned value of ptr (which may be NULL on
> > failure). For cases where the total size of the allocation is needed,
> > the kmalloc_obj_sz(), kmalloc_objs_sz(), and kmalloc_flex_sz() family
> > of macros can be used. For example:
> > 
> > 	info->size = struct_size(ptr, flex_member, count);
> > 	ptr = kmalloc(info->size, gfp);
> > 
> > becomes:
> > 
> > 	kmalloc_flex_sz(ptr, flex_member, count, gfp, &info->size);
> 
> I wonder if it'd be better to keep the gfp flags as the last argument
> for all these `*_sz()` cases:
> 
> 	kmalloc_flex_sz(ptr, flex_member, count, &info->size, gpf);
> 
> Probably, even for __alloc_objs()

I was following the pattern of the other "alternative helpers", like
kmalloc_node(), which adds the additional argument to the end. I have no
real opinion about it, so I defer to the slab developers. :)

-Kees

-- 
Kees Cook