[PATCH AUTOSEL 4.20 39/60] kasan, slab: make freelist stored without tags

[Sasha Levin]

From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

[ 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@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Tested-by: Qian Cai <cai@xxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgeniy Stepanov <eugenis@xxxxxxxxxx>
Cc: Kostya Serebryany <kcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/slab.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index 05f21f736be8..b85524f2ab35 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2381,6 +2381,7 @@ 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 {
@@ -2694,6 +2695,13 @@ 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);
@@ -2702,7 +2710,6 @@ 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