On Thu, Aug 04, 2022 at 06:47:58PM +0800, Dmitry Vyukov wrote: > On Thu, 4 Aug 2022 at 08:29, Feng Tang <feng.tang@xxxxxxxxx> wrote: [...] > > > > ---8<--- > > From c4fc739ea4d5222f0aba4b42b59668d64a010082 Mon Sep 17 00:00:00 2001 > > From: Feng Tang <feng.tang@xxxxxxxxx> > > Date: Thu, 4 Aug 2022 13:25:35 +0800 > > Subject: [PATCH] mm: kasan: Add free_meta size info in struct kasan_cache > > > > When kasan is enabled for slab/slub, it may save kasan' free_meta > > data in the former part of slab object data area in slab object > > free path, which works fine. > > > > There is ongoing effort to extend slub's debug function which will > > redzone the latter part of kmalloc object area, and when both of > > the debug are enabled, there is possible conflict, especially when > > the kmalloc object has small size, as caught by 0Day bot [1] > > > > For better information for slab/slub, add free_meta's data size > > info 'kasan_cache', so that its users can take right action to > > avoid data conflict. > > > > [1]. https://lore.kernel.org/lkml/YuYm3dWwpZwH58Hu@xsang-OptiPlex-9020/ > > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> > > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > > Acked-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Thanks for your suggestion and review! > I assume there will be a second patch that uses > free_meta_size_in_object in slub debug code. Yes, it will be called in the slub kmalloc object redzone debug code. Thanks, Feng > > --- > > include/linux/kasan.h | 2 ++ > > mm/kasan/common.c | 2 ++ > > 2 files changed, 4 insertions(+) > > > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > > index b092277bf48d..293bdaa0ba09 100644 > > --- a/include/linux/kasan.h > > +++ b/include/linux/kasan.h > > @@ -100,6 +100,8 @@ static inline bool kasan_has_integrated_init(void) > > struct kasan_cache { > > int alloc_meta_offset; > > int free_meta_offset; > > + /* size of free_meta data saved in object's data area */ > > + int free_meta_size_in_object; > > bool is_kmalloc; > > }; > > > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > > index 78be2beb7453..a627efa267d1 100644 > > --- a/mm/kasan/common.c > > +++ b/mm/kasan/common.c > > @@ -201,6 +201,8 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size, > > cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META; > > *size = ok_size; > > } > > + } else { > > + cache->kasan_info.free_meta_size_in_object = sizeof(struct kasan_free_meta); > > } > > > > /* Calculate size with optimal redzone. */ > > -- > > 2.27.0 >
