[PATCH] mm/slab: always use cache from obj

["Jiazi.Li" <jqqlijiazi@gmail.com>]

If free obj to a wrong cache, in addition random, different offset
and object_size will also cause problems:
1. The offset of a cache with a ctor is not zero, free an object from
this cache to cache with offset zero, will write next freepointer to
wrong location, resulting in confusion of freelist.
2. If wrong cache want init on free, and cache->object_size is large
than obj size, which may lead to overwrite issue.

Compared with adding a lot of if-else, it may be better to use obj's
cache directly.

Signed-off-by: Jiazi.Li <jiazi.li@transsion.com>
---
 mm/slab.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 63fb4c00d529..ed39b2e4f27b 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -670,10 +670,6 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
 {
 	struct kmem_cache *cachep;
 
-	if (!IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
-	    !kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS))
-		return s;
-
 	cachep = virt_to_cache(x);
 	if (WARN(cachep && cachep != s,
 		  "%s: Wrong slab cache. %s but object is from %s\n",
-- 
2.17.1