Re: [PATCH v1] slab: support for compiler-assisted type-based slab cache partitioning

Dan Carpenter
2026-04-02T17:05:39Z

On Thu, Apr 02, 2026 at 03:48:20PM +0200, Marco Elver wrote:
> On Thu, 2 Apr 2026 at 15:33, Dan Carpenter <error27@gmail.com> wrote:
> >
> > Hi Marco,
> >
> > kernel test robot noticed the following build warnings:
> >
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url: https://github.com/intel-lab-lkp/linux/commits/Marco-Elver/slab-support-for-compiler-assisted-type-based-slab-cache-partitioning/20260401-035608
> > base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> > patch link: https://lore.kernel.org/r/20260331111240.153913-1-elver%40google.com
> > patch subject: [PATCH v1] slab: support for compiler-assisted type-based slab cache partitioning
> > config: um-randconfig-r072-20260401
> > compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
> > smatch: v0.5.0-9004-gb810ac53
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <error27@gmail.com>
> > | Closes: https://lore.kernel.org/r/202604020400.jEq32K95-lkp@intel.com/
> >
> > New smatch warnings:
> > drivers/misc/lkdtm/heap.c:118 lkdtm_READ_AFTER_FREE() warn: potential pointer math issue ('base' is a 32 bit pointer)
> > drivers/misc/lkdtm/heap.c:169 lkdtm_KFENCE_READ_AFTER_FREE() warn: potential pointer math issue ('base' is a 32 bit pointer)
>
> How is this related to the patch I sent? Did the <linux/slab.h> change
> force rechecking of all these files and it found latent issues?
>

Oh, crud. It turns out that for this check Smatch allows
integer_array[sizeof()]so long as we know that the index is within
bounds. What happened is that your patch renamed the kmalloc()
function so Smatch stopped knowing the size of the buffer.

For these zero day bot warnings, the emails are automatically generated
so I don't have any context outside what's in the email. I saw that
Kees wrote the code, but I figured maybe you forwarded it or something.
Sorry about that.

regards,
dan carpenter