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@lca.pw: arm64: skip kmemleak for KASAN again\
Link: http://lkml.kernel.org/r/20181226020550.63712-1-cai@lca.pw
Link: http://lkml.kernel.org/r/5cc1b789aad7c99cf4f3ec5b328b147ad53edb40.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 4ebc19422931b161da14fc5a6e3b32a4fa5c07cc..38fa4bba92796f34a801f4253560e6bba2e90ae5 100644 (file)
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -43,6 +43,14 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
        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(pmd_t *pmdp, unsigned long addr,
        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 */

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index ec22d548d0d70bb57d756307fe5ea597063a9a10..c56af24bd3e79920f64df4cb2ccf2da638cd7ac3 100644 (file)
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -153,6 +153,8 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
 
 #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(struct kmem_cache *cache) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 
+#ifdef CONFIG_KASAN_SW_TAGS
+
+#define KASAN_SHADOW_INIT 0xFF
+
+#endif /* CONFIG_KASAN_SW_TAGS */
+
 #endif /* LINUX_KASAN_H */

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 5f68c93734bab5f1157b6c1119e5a12a14899457..7134e75447ff9d078af959cce5bdee9d9625b964 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -473,11 +473,12 @@ int kasan_module_alloc(void *addr, size_t 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;