Commit adef2aea authored by Chengming Zhou's avatar Chengming Zhou Committed by Vlastimil Babka
Browse files

slab: don't put freepointer outside of object if only orig_size 



The commit 946fa0db ("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: default avatarFeng Tang <feng.tang@intel.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
parent 47d911b0

mm/slub.c

+6 −5
Original line number Diff line number Diff line
@@ -5167,10 +5167,9 @@ 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
@@ -5178,7 +5177,9 @@ 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