arm64: kasan: fix page_alloc tagging with DEBUG_VIRTUAL

When CONFIG_DEBUG_VIRTUAL is enabled, the default page_to_virt() macro
implementation from include/linux/mm.h is used. That definition doesn't
account for KASAN tags, which leads to no tags on page_alloc allocations.

Provide an arm64-specific definition for page_to_virt() when
CONFIG_DEBUG_VIRTUAL is enabled that takes care of KASAN tags.

Fixes: 2813b9c0 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc")
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/4b55b35202706223d3118230701c6a59749d9b72.1615219501.git.andreyknvl@google.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/memory.h

@@ -328,6 +328,11 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define ARCH_PFN_OFFSET		((unsigned long)PHYS_PFN_OFFSET)
 
 #if !defined(CONFIG_SPARSEMEM_VMEMMAP) || defined(CONFIG_DEBUG_VIRTUAL)
+#define page_to_virt(x)	({						\
+	__typeof__(x) __page = x;					\
+	void *__addr = __va(page_to_phys(__page));			\
+	(void *)__tag_set((const void *)__addr, page_kasan_tag(__page));\
+})
 #define virt_to_page(x)		pfn_to_page(virt_to_pfn(x))
 #else
 #define page_to_virt(x)	({						\