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

[Oliver Sang <oliver.sang@intel.com>]

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:

=========================================================================================
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;
>  
> 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@intel.com> wrote:
> > [...]
> > > >
> > > > ---8<---
> > > > From c4fc739ea4d5222f0aba4b42b59668d64a010082 Mon Sep 17 00:00:00 2001
> > > > From: Feng Tang <feng.tang@intel.com>
> > > > 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@intel.com>
> > > > Signed-off-by: Feng Tang <feng.tang@intel.com>
> > > 
> > > Acked-by: Dmitry Vyukov <dvyukov@google.com>
> >  
> > 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
> > >