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

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The commit 946fa0dbf2 ("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>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Chengming Zhou 2024-06-07 16:40:13 +08:00 • committed by Vlastimil Babka
parent 47d911b02c
commit adef2aeaa2
1 changed files with 6 additions and 5 deletions
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11
mm/slub.c
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@ -5167,10 +5167,9 @@ static int calculate_sizes(struct kmem_cache *s)
*/ */
s->inuse = size; s->inuse = size;
if (slub_debug_orig_size(s) || if ((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || s->ctor ||
(flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) || ((flags & SLAB_RED_ZONE) &&
((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) || (s->object_size < sizeof(void *) || slub_debug_orig_size(s)))) {
s->ctor) {
/* /*
* Relocate free pointer after the object if it is not * Relocate free pointer after the object if it is not
* permitted to overwrite the first word of the object on * 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 * This is the case if we do RCU, have a constructor or
* destructor, are poisoning the objects, or are * 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 * The assumption that s->offset >= s->inuse means free
* pointer is outside of the object is used in the * pointer is outside of the object is used in the