Re: [mm/slub] 3616799128: BUG_kmalloc-#(Not_tainted):kmalloc_Redzone_overwritten

Feng Tang
2022-08-16T14:13:20Z

On Tue, Aug 16, 2022 at 09:27:39PM +0800, Sang, Oliver wrote:
> Hi Feng,
>
> On Mon, Aug 15, 2022 at 03:27:43PM +0800, Feng Tang wrote:
> > Hi Oliver,
> >
> > Could you help to check if the below combined patch fix the problem
> > you reported? thanks!
>
> I applied below patch upon 3616799128:
> 28b34693c816e9 (linux-devel/fixup-3616799128) fix for 3616799128: BUG_kmalloc-#(Not_tainted):kmalloc_Redzone_overwritten
> 3616799128612e (linux-review/Feng-Tang/mm-slub-some-debug-enhancements/20220727-151318) mm/slub: extend redzone check to cover extra allocated kmalloc space than requested
> acc77d62f91ccc mm/slub: only zero the requested size of buffer for kzalloc
>
>
> confirmed the issue gone:

Many thanks for helping testing!

- Feng

> =========================================================================================
> compiler/kconfig/rootfs/sleep/tbox_group/testcase:
> gcc-11/x86_64-randconfig-a005-20220117/debian-11.1-x86_64-20220510.cgz/300/vm-snb/boot
>
>
> acc77d62f91ccca2 3616799128612e04ed919579e2c 28b34693c816e9fcbe42bdd341e
> ---------------- --------------------------- ---------------------------
> fail:runs %reproduction fail:runs %reproduction fail:runs
> | | | | |
> :20 95% 19:20 0% :22 dmesg.BUG_kmalloc-#(Not_tainted):kmalloc_Redzone_overwritten
> :20 95% 19:20 0% :22 dmesg.BUG_kmalloc-#(Tainted:G_B):kmalloc_Redzone_overwritten
>
>
>
> >
> > - 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;
> >