Re: [PATCH v3 2/6] mm/slab: Plumb kmem_buckets into __do_kmalloc_node()

[Kees Cook <kees@kernel.org>]

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@chromium.org>
> > ---
> > Cc: Vlastimil Babka <vbabka@suse.cz>
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: Pekka Enberg <penberg@kernel.org>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Roman Gushchin <roman.gushchin@linux.dev>
> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> > Cc: linux-mm@kvack.org
> > Cc: linux-hardening@vger.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