On Mon, Aug 28, 2023 at 4:40 PM Jann Horn <jannh@xxxxxxxxxx> wrote: > > > Can't we unpoision this rcu_head right before call_rcu() and repoison > > after receiving the callback? > > Yeah, I think that should work. It looks like currently > kasan_unpoison() is exposed in include/linux/kasan.h but > kasan_poison() is not, and its inline definition probably means I > can't just move it out of mm/kasan/kasan.h into include/linux/kasan.h; > do you have a preference for how I should handle this? Hmm, and it > also looks like code outside of mm/kasan/ anyway wouldn't know what > are valid values for the "value" argument to kasan_poison(). > I also have another feature idea that would also benefit from having > something like kasan_poison() available in include/linux/kasan.h, so I > would prefer that over adding another special-case function inside > KASAN for poisoning this piece of slab metadata... This is a problem only for the Generic mode, right? You already call kasan_reset_tag on the rcu_head, which should suppress the reporting for the tag-based modes. If so, would it be possible to reuse metadata_access_enable/disable? They are used for accessing slub_debug metadata and seem to fit nicely with this case as well. I also second Macro's comment to add a test for the new functionality. Thanks for working on this!
