linux-hardening - [PATCH 2/2] mm/slub: remove freelist

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Message-ID: <20230711134623.12695-4-vbabka@suse.cz>
Date:   Tue, 11 Jul 2023 15:46:25 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Matteo Rizzo <matteorizzo@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev@...glegroups.com, Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 2/2] mm/slub: remove freelist_dereference()

freelist_dereference() is a one-liner only used from get_freepointer().
Remove it and make get_freepointer() call freelist_ptr_decode()
directly to make the code easier to follow.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 07edad305512..c4556a5dab4b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -397,18 +397,14 @@ static inline void *freelist_ptr_decode(const struct kmem_cache *s,
 	return decoded;
 }
 
-/* Returns the freelist pointer recorded at location ptr_addr. */
-static inline void *freelist_dereference(const struct kmem_cache *s,
-					 void *ptr_addr)
-{
-	return freelist_ptr_decode(s, *(freeptr_t *)(ptr_addr),
-			    (unsigned long)ptr_addr);
-}
-
 static inline void *get_freepointer(struct kmem_cache *s, void *object)
 {
-	object = kasan_reset_tag(object);
-	return freelist_dereference(s, (freeptr_t *)(object + s->offset));
+	unsigned long ptr_addr;
+	freeptr_t p;
+
+	ptr_addr = ((unsigned long)kasan_reset_tag(object)) + s->offset;
+	p = *(freeptr_t *)(ptr_addr);
+	return freelist_ptr_decode(s, p, ptr_addr);
 }
 
 #ifndef CONFIG_SLUB_TINY
-- 
2.41.0