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 11:01:40AM -0400, Kent Overstreet wrote:
> On Wed, Apr 24, 2024 at 02:40:59PM -0700, 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().
> 
> I thought the plan was to use codetags for this? That would obviate the
> need for all this plumbing.
> 
> Add fields to the alloc tag for:
>  - allocation size (or 0 if it's not a compile time constant)
>  - union of kmem_cache, kmem_buckets, depending on whether the
>    allocation size is constant or not

I want to provide "simple" (low-hanging fruit) coverage that can live
separately from the codetags-based coverage. The memory overhead for
this patch series is negligible, but I suspect the codetags expansion,
while not giant, will be more than some deployments will want. I want
to avoid an all-or-nothing solution -- which is why I had intended this
to be available "by default".

But I will respin this with kmem_buckets under a Kconfig.

-- 
Kees Cook