Re: [PATCH v2 0/5] mm/slub: Improve data handling of krealloc() when orig_size is enabled

[Kees Cook]

On Mon, Oct 14, 2024 at 10:20:36PM +0800, Feng Tang wrote:
> On Mon, Oct 14, 2024 at 03:12:09PM +0200, Vlastimil Babka wrote:
> > On 10/14/24 14:52, Feng Tang wrote:
> > > On Mon, Oct 14, 2024 at 10:53:32AM +0200, Vlastimil Babka wrote:
> > >> On 10/14/24 09:52, Feng Tang wrote:
> > > OK, originally I tried not to expose internals of __ksize(). Let me
> > > try this way.
> > 
> > ksize() makes assumptions that a user outside of slab itself is calling it.
> > 
> > But we (well mostly Kees) also introduced kmalloc_size_roundup() to avoid
> > querying ksize() for the purposes of writing beyond the original
> > kmalloc(size) up to the bucket size. So maybe we can also investigate if the
> > skip_orig_size_check() mechanism can be removed now?
> 
> I did a quick grep, and fortunately it seems that the ksize() user are
> much less than before. We used to see some trouble in network code, which
> is now very clean without the need to skip orig_size check. Will check
> other call site later.

Right -- only things that are performing a reallocation should be using
ksize(). e.g. see __slab_build_skb()

-- 
Kees Cook