[PATCH AUTOSEL 4.20 38/60] kasan, slab: fix conflicts with CONFIG_HARDENED_USERCOPY

[Sasha Levin]

From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

[ Upstream commit 219667c23c68eb3dbc0d5662b9246f28477fe529 ]

Similarly to commit 96fedce27e13 ("kasan: make tag based mode work with
CONFIG_HARDENED_USERCOPY"), we need to reset pointer tags in
__check_heap_object() in mm/slab.c before doing any pointer math.

Link: http://lkml.kernel.org/r/9a5c0f958db10e69df5ff9f2b997866b56b7effc.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 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/slab.c b/mm/slab.c
index 9d5de959d9d9..05f21f736be8 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4421,6 +4421,8 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 	unsigned int objnr;
 	unsigned long offset;
 
+	ptr = kasan_reset_tag(ptr);
+
 	/* Find and validate object. */
 	cachep = page->slab_cache;
 	objnr = obj_to_index(cachep, page, (void *)ptr);
-- 
2.19.1