From 346907ceb9d11b9e22677c142b45ff50dd20a66a Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Wed, 16 Nov 2022 15:56:32 +0100 Subject: mm, slab: ignore hardened usercopy parameters when disabled With CONFIG_HARDENED_USERCOPY not enabled, there are no __check_heap_object() checks happening that would use the struct kmem_cache useroffset and usersize fields. Yet the fields are still initialized, preventing merging of otherwise compatible caches. Also the fields contribute to struct kmem_cache size unnecessarily when unused. Thus #ifdef them out completely when CONFIG_HARDENED_USERCOPY is disabled. In kmem_dump_obj() print object_size instead of usersize, as that's actually the intention. In a quick virtme boot test, this has reduced the number of caches in /proc/slabinfo from 131 to 111. Cc: Kees Cook Signed-off-by: Vlastimil Babka Acked-by: Roman Gushchin Acked-by: Mike Rapoport Reviewed-by: Christoph Lameter --- mm/slub.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'mm/slub.c') diff --git a/mm/slub.c b/mm/slub.c index 157527d7101b..e32db8540767 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5502,11 +5502,13 @@ static ssize_t cache_dma_show(struct kmem_cache *s, char *buf) SLAB_ATTR_RO(cache_dma); #endif +#ifdef CONFIG_HARDENED_USERCOPY static ssize_t usersize_show(struct kmem_cache *s, char *buf) { return sysfs_emit(buf, "%u\n", s->usersize); } SLAB_ATTR_RO(usersize); +#endif static ssize_t destroy_by_rcu_show(struct kmem_cache *s, char *buf) { @@ -5803,7 +5805,9 @@ static struct attribute *slab_attrs[] = { #ifdef CONFIG_FAILSLAB &failslab_attr.attr, #endif +#ifdef CONFIG_HARDENED_USERCOPY &usersize_attr.attr, +#endif #ifdef CONFIG_KFENCE &skip_kfence_attr.attr, #endif -- cgit v1.2.3