kasan, mm, arm64: tag non slab memory allocated via pagealloc

Tag-based KASAN doesn't check memory accesses through pointers tagged with
0xff.  When page_address is used to get pointer to memory that corresponds
to some page, the tag of the resulting pointer gets set to 0xff, even
though the allocated memory might have been tagged differently.

For slab pages it's impossible to recover the correct tag to return from
page_address, since the page might contain multiple slab objects tagged
with different values, and we can't know in advance which one of them is
going to get accessed.  For non slab pages however, we can recover the tag
in page_address, since the whole page was marked with the same tag.

This patch adds tagging to non slab memory allocated with pagealloc.  To
set the tag of the pointer returned from page_address, the tag gets stored
to page->flags when the memory gets allocated.

Link: http://lkml.kernel.org/r/d758ddcef46a5abc9970182b9137e2fbee202a2c.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>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 27f0cae336c9..195ca385cf7a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -220,8 +220,15 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
 
 void kasan_alloc_pages(struct page *page, unsigned int order)
 {
+	u8 tag;
+	unsigned long i;
+
 	if (unlikely(PageHighMem(page)))
 		return;
+
+	tag = random_tag();
+	for (i = 0; i < (1 << order); i++)
+		page_kasan_tag_set(page + i, tag);
 	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 }
 
@@ -319,6 +326,10 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 
 void kasan_poison_slab(struct page *page)
 {
+	unsigned long i;
+
+	for (i = 0; i < (1 << compound_order(page)); i++)
+		page_kasan_tag_reset(page + i);
 	kasan_poison_shadow(page_address(page),
 			PAGE_SIZE << compound_order(page),
 			KASAN_KMALLOC_REDZONE);
@@ -517,7 +528,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 	page = virt_to_head_page(ptr);
 
 	if (unlikely(!PageSlab(page))) {
-		if (reset_tag(ptr) != page_address(page)) {
+		if (ptr != page_address(page)) {
 			kasan_report_invalid_free(ptr, ip);
 			return;
 		}
@@ -530,7 +541,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 
 void kasan_kfree_large(void *ptr, unsigned long ip)
 {
-	if (reset_tag(ptr) != page_address(virt_to_head_page(ptr)))
+	if (ptr != page_address(virt_to_head_page(ptr)))
 		kasan_report_invalid_free(ptr, ip);
 	/* The object will be poisoned by page_alloc. */
 }