Hi Oliver, Could you help to check if the below combined patch fix the problem you reported? thanks! - Feng --- diff --git a/include/linux/kasan.h b/include/linux/kasan.h index b092277bf48d6..293bdaa0ba09c 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 c40c0e7b3b5f1..9d2994dbe4e7a 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -200,6 +200,8 @@ 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. */ diff --git a/mm/slub.c b/mm/slub.c index added2653bb03..272dcdbaaa03b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -830,6 +830,16 @@ static inline void set_orig_size(struct kmem_cache *s, if (!slub_debug_orig_size(s)) return; +#ifdef CONFIG_KASAN_GENERIC + /* + * kasn could save its free meta data in the start part of object + * area, so skip the redzone check if kasan's meta data size is + * bigger enough to possibly overlap with kmalloc redzone + */ + if (s->kasan_info.free_meta_size_in_object * 2 > s->object_size) + orig_size = s->object_size; +#endif + p += get_info_end(s); p += sizeof(struct track) * 2; On Thu, Aug 04, 2022 at 08:22:31PM +0800, Tang, Feng wrote: > 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 > >