| Message ID | 20240605-b4-slab-debug-v2-2-c535b9cd361c@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | slab: fix and cleanup of slub_debug | expand |
On 6/5/24 9:13 AM, Chengming Zhou wrote: > The commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra > allocated kmalloc space than requested") will extend right redzone > when allocating for orig_size < object_size. So we can't overlay the > freepointer in the object space in this case. > > But the code looks like it forgot to check SLAB_RED_ZONE, since there > won't be extended right redzone if only orig_size enabled. > > As we are here, make this complex conditional expressions a little > prettier and add some comments about extending right redzone when > slub_debug_orig_size() enabled. > > Reviewed-by: Feng Tang <feng.tang@intel.com> > Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/slub.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 7fbd5ce4320a..704c662227e6 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5152,10 +5152,9 @@ static int calculate_sizes(struct kmem_cache *s) > */ > s->inuse = size; > > - if (slub_debug_orig_size(s) || > - (flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || > - ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) || > - s->ctor) { > + if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || s->ctor || > + ((flags & SLAB_RED_ZONE) && > + (s->object_size < sizeof(void *) || slub_debug_orig_size(s)))) { > /* > * Relocate free pointer after the object if it is not > * permitted to overwrite the first word of the object on > @@ -5163,7 +5162,9 @@ static int calculate_sizes(struct kmem_cache *s) > * > * This is the case if we do RCU, have a constructor or > * destructor, are poisoning the objects, or are > - * redzoning an object smaller than sizeof(void *). > + * redzoning an object smaller than sizeof(void *) or are > + * redzoning an object with slub_debug_orig_size() enabled, > + * in which case the right redzone may be extended. > * > * The assumption that s->offset >= s->inuse means free > * pointer is outside of the object is used in the >
diff --git a/mm/slub.c b/mm/slub.c index 7fbd5ce4320a..704c662227e6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5152,10 +5152,9 @@ static int calculate_sizes(struct kmem_cache *s) */ s->inuse = size; - if (slub_debug_orig_size(s) || - (flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || - ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) || - s->ctor) { + if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || s->ctor || + ((flags & SLAB_RED_ZONE) && + (s->object_size < sizeof(void *) || slub_debug_orig_size(s)))) { /* * Relocate free pointer after the object if it is not * permitted to overwrite the first word of the object on @@ -5163,7 +5162,9 @@ static int calculate_sizes(struct kmem_cache *s) * * This is the case if we do RCU, have a constructor or * destructor, are poisoning the objects, or are - * redzoning an object smaller than sizeof(void *). + * redzoning an object smaller than sizeof(void *) or are + * redzoning an object with slub_debug_orig_size() enabled, + * in which case the right redzone may be extended. * * The assumption that s->offset >= s->inuse means free * pointer is outside of the object is used in the
The commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated kmalloc space than requested") will extend right redzone when allocating for orig_size < object_size. So we can't overlay the freepointer in the object space in this case. But the code looks like it forgot to check SLAB_RED_ZONE, since there won't be extended right redzone if only orig_size enabled. As we are here, make this complex conditional expressions a little prettier and add some comments about extending right redzone when slub_debug_orig_size() enabled. Reviewed-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> --- mm/slub.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)