kasan, slab: make freelist stored without tags

Similarly to "kasan, slub: move kasan_poison_slab hook before
page_address", move kasan_poison_slab() before alloc_slabmgmt(), which
calls page_address(), to make page_address() return value to be
non-tagged.  This, combined with calling kasan_reset_tag() for off-slab
slab management object, leads to freelist being stored non-tagged.

Link: http://lkml.kernel.org/r/dfb53b44a4d00de3879a05a9f04c1f55e584f7a1.1550602886.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Qian Cai <cai@lca.pw>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgeniy Stepanov <eugenis@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slab.c b/mm/slab.c
index c84458281a8866b7ab880609bead7ccc0be79a83..4ad95fcb16869c441a3f84419be836048d8b8586 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2359,7 +2359,7 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep,
        void *freelist;
        void *addr = page_address(page);
 
-       page->s_mem = kasan_reset_tag(addr) + colour_off;
+       page->s_mem = addr + colour_off;
        page->active = 0;
 
        if (OBJFREELIST_SLAB(cachep))
@@ -2368,6 +2368,7 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep,
                /* Slab management obj is off-slab. */
                freelist = kmem_cache_alloc_node(cachep->freelist_cache,
                                              local_flags, nodeid);
+               freelist = kasan_reset_tag(freelist);
                if (!freelist)
                        return NULL;
        } else {
@@ -2681,6 +2682,13 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
 
        offset *= cachep->colour_off;
 
+       /*
+        * Call kasan_poison_slab() before calling alloc_slabmgmt(), so
+        * page_address() in the latter returns a non-tagged pointer,
+        * as it should be for slab pages.
+        */
+       kasan_poison_slab(page);
+
        /* Get slab management. */
        freelist = alloc_slabmgmt(cachep, page, offset,
                        local_flags & ~GFP_CONSTRAINT_MASK, page_node);
@@ -2689,7 +2697,6 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
 
        slab_map_pages(cachep, page, freelist);
 
-       kasan_poison_slab(page);
        cache_init_objs(cachep, page);
 
        if (gfpflags_allow_blocking(local_flags))