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Subject[PATCH AUTOSEL 4.14 22/33] kasan, slab: make freelist stored without tags
Date
From: Andrey Konovalov <andreyknvl@google.com>

[ Upstream commit 51dedad06b5f6c3eea7ec1069631b1ef7796912a ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/slab.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index 409631e49295..766043dd3f8e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2378,6 +2378,7 @@ 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 {
@@ -2690,6 +2691,13 @@ 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);
@@ -2698,7 +2706,6 @@ 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))
--
2.19.1
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