On Mon, 17 Jul 2017, Alexander Popov wrote: > Add an assertion similar to "fasttop" check in GNU C Library allocator: > an object added to a singly linked freelist should not point to itself. > That helps to detect some double free errors (e.g. CVE-2017-2636) without > slub_debug and KASAN. Testing with hackbench doesn't show any noticeable > performance penalty.
We are adding up "unnoticable performance penalties". This is used int both the critical allocation and free paths. Could this be VM_BUG_ON()? > > Signed-off-by: Alexander Popov <[email protected]> > --- > mm/slub.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/slub.c b/mm/slub.c > index 1d3f983..a106939b 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -261,6 +261,7 @@ static inline void *get_freepointer_safe(struct > kmem_cache *s, void *object) > > static inline void set_freepointer(struct kmem_cache *s, void *object, void > *fp) > { > + BUG_ON(object == fp); /* naive detection of double free or corruption */ > *(void **)(object + s->offset) = fp; > } > >
