linux-hardening - Re: [PATCH v3 2/6] mm/slab: Plumb kmem_buckets into __do_kmalloc

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Message-ID: <202405310941.62F7B2859C@keescook>
Date: Fri, 31 May 2024 09:42:59 -0700
From: Kees Cook <kees@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: 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>, linux-mm@...ck.org,
	linux-hardening@...r.kernel.org,
	"GONG, Ruiqi" <gongruiqi@...weicloud.com>,
	Xiu Jianfeng <xiujianfeng@...wei.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Jann Horn <jannh@...gle.com>, Matteo Rizzo <matteorizzo@...gle.com>,
	Thomas Graf <tgraf@...g.ch>,
	Herbert Xu <herbert@...dor.apana.org.au>, julien.voisin@...tri.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/6] mm/slab: Plumb kmem_buckets into
 __do_kmalloc_node()

On Fri, May 24, 2024 at 03:38:58PM +0200, Vlastimil Babka wrote:
> On 4/24/24 11:40 PM, Kees Cook wrote:
> > To be able to choose which buckets to allocate from, make the buckets
> > available to the lower level kmalloc interfaces by adding them as the
> > first argument. Where the bucket is not available, pass NULL, which means
> > "use the default system kmalloc bucket set" (the prior existing behavior),
> > as implemented in kmalloc_slab().
> > 
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> > Cc: Vlastimil Babka <vbabka@...e.cz>
> > Cc: Christoph Lameter <cl@...ux.com>
> > Cc: Pekka Enberg <penberg@...nel.org>
> > Cc: David Rientjes <rientjes@...gle.com>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Roman Gushchin <roman.gushchin@...ux.dev>
> > Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
> > Cc: linux-mm@...ck.org
> > Cc: linux-hardening@...r.kernel.org
> > ---
> >  include/linux/slab.h | 16 ++++++++--------
> >  lib/fortify_kunit.c  |  2 +-
> >  mm/slab.h            |  6 ++++--
> >  mm/slab_common.c     |  4 ++--
> >  mm/slub.c            | 14 +++++++-------
> >  mm/util.c            |  2 +-
> >  6 files changed, 23 insertions(+), 21 deletions(-)
> > 
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index c8164d5db420..07373b680894 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -569,8 +569,8 @@ static __always_inline void kfree_bulk(size_t size, void **p)
> >  	kmem_cache_free_bulk(NULL, size, p);
> >  }
> >  
> > -void *__kmalloc_node_noprof(size_t size, gfp_t flags, int node) __assume_kmalloc_alignment
> > -							 __alloc_size(1);
> > +void *__kmalloc_node_noprof(kmem_buckets *b, size_t size, gfp_t flags, int node)
> > +				__assume_kmalloc_alignment __alloc_size(2);
> >  #define __kmalloc_node(...)			alloc_hooks(__kmalloc_node_noprof(__VA_ARGS__))
> >  
> >  void *kmem_cache_alloc_node_noprof(struct kmem_cache *s, gfp_t flags,
> > @@ -679,7 +679,7 @@ static __always_inline __alloc_size(1) void *kmalloc_node_noprof(size_t size, gf
> >  				kmalloc_caches[kmalloc_type(flags, _RET_IP_)][index],
> >  				flags, node, size);
> >  	}
> > -	return __kmalloc_node_noprof(size, flags, node);
> > +	return __kmalloc_node_noprof(NULL, size, flags, node);
> 
> This is not ideal as now every kmalloc_node() callsite will now have to add
> the NULL parameter even if this is not enabled. Could the new parameter be
> only added depending on the respective config?

I felt like it was much simpler to add an argument to the existing call
path than to create a duplicate API that had 1 extra argument. However,
if you want this behind a Kconfig option, I can redefine the argument
list based on that?

-- 
Kees Cook