From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: kasan: initialize shadow to 0xff for tag-based mode A tag-based KASAN shadow memory cell contains a memory tag, that corresponds to the tag in the top byte of the pointer, that points to that memory. The native top byte value of kernel pointers is 0xff, so with tag-based KASAN we need to initialize shadow memory to 0xff. [cai@xxxxxx: arm64: skip kmemleak for KASAN again\ Link: http://lkml.kernel.org/r/20181226020550.63712-1-cai@xxxxxx Link: http://lkml.kernel.org/r/5cc1b789aad7c99cf4f3ec5b328b147ad53edb40.1544099024.git.andreyknvl@xxxxxxxxxx Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- --- a/arch/arm64/mm/kasan_init.c~kasan-initialize-shadow-to-0xff-for-tag-based-mode +++ a/arch/arm64/mm/kasan_init.c @@ -43,6 +43,14 @@ static phys_addr_t __init kasan_alloc_ze return __pa(p); } +static phys_addr_t __init kasan_alloc_raw_page(int node) +{ + void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE, + __pa(MAX_DMA_ADDRESS), + MEMBLOCK_ALLOC_KASAN, node); + return __pa(p); +} + static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node, bool early) { @@ -92,7 +100,9 @@ static void __init kasan_pte_populate(pm do { phys_addr_t page_phys = early ? __pa_symbol(kasan_early_shadow_page) - : kasan_alloc_zeroed_page(node); + : kasan_alloc_raw_page(node); + if (!early) + memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE); next = addr + PAGE_SIZE; set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL)); } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep))); @@ -239,7 +249,7 @@ void __init kasan_init(void) pfn_pte(sym_to_pfn(kasan_early_shadow_page), PAGE_KERNEL_RO)); - memset(kasan_early_shadow_page, 0, PAGE_SIZE); + memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE); cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); /* At this point kasan is fully initialized. Enable error messages */ --- a/include/linux/kasan.h~kasan-initialize-shadow-to-0xff-for-tag-based-mode +++ a/include/linux/kasan.h @@ -153,6 +153,8 @@ static inline size_t kasan_metadata_size #ifdef CONFIG_KASAN_GENERIC +#define KASAN_SHADOW_INIT 0 + void kasan_cache_shrink(struct kmem_cache *cache); void kasan_cache_shutdown(struct kmem_cache *cache); @@ -163,4 +165,10 @@ static inline void kasan_cache_shutdown( #endif /* CONFIG_KASAN_GENERIC */ +#ifdef CONFIG_KASAN_SW_TAGS + +#define KASAN_SHADOW_INIT 0xFF + +#endif /* CONFIG_KASAN_SW_TAGS */ + #endif /* LINUX_KASAN_H */ --- a/mm/kasan/common.c~kasan-initialize-shadow-to-0xff-for-tag-based-mode +++ a/mm/kasan/common.c @@ -473,11 +473,12 @@ int kasan_module_alloc(void *addr, size_ ret = __vmalloc_node_range(shadow_size, 1, shadow_start, shadow_start + shadow_size, - GFP_KERNEL | __GFP_ZERO, + GFP_KERNEL, PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE, __builtin_return_address(0)); if (ret) { + __memset(ret, KASAN_SHADOW_INIT, shadow_size); find_vm_area(addr)->flags |= VM_KASAN; kmemleak_ignore(ret); return 0; _
