kasan, mm: integrate page_alloc init with HW_TAGS

This change uses the previously added memory initialization feature of
HW_TAGS KASAN routines for page_alloc memory when init_on_alloc/free is
enabled.

With this change, kernel_init_free_pages() is no longer called when both
HW_TAGS KASAN and init_on_alloc/free are enabled.  Instead, memory is
initialized in KASAN runtime.

To avoid discrepancies with which memory gets initialized that can be
caused by future changes, both KASAN and kernel_init_free_pages() hooks
are put together and a warning comment is added.

This patch changes the order in which memory initialization and page
poisoning hooks are called.  This doesn't lead to any side-effects, as
whenever page poisoning is enabled, memory initialization gets disabled.

Combining setting allocation tags with memory initialization improves
HW_TAGS KASAN performance when init_on_alloc/free is enabled.

[andreyknvl@google.com: fix for "integrate page_alloc init with HW_TAGS"]
  Link: https://lkml.kernel.org/r/65b6028dea2e9a6e8e2cb779b5115c09457363fc.1617122211.git.andreyknvl@google.com

Link: https://lkml.kernel.org/r/e77f0d5b1b20658ef0b8288625c74c2b3690e725.1615296150.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Tested-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@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>

1 files changed, 31 insertions, 10 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 342cabf912a7..6314de5387f5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -397,14 +397,14 @@ static DEFINE_STATIC_KEY_TRUE(deferred_pages);
  * initialization is done, but this is not likely to happen.
  */
 static inline void kasan_free_nondeferred_pages(struct page *page, int order,
-							fpi_t fpi_flags)
+						bool init, fpi_t fpi_flags)
 {
 	if (static_branch_unlikely(&deferred_pages))
 		return;
 	if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
 			(fpi_flags & FPI_SKIP_KASAN_POISON))
 		return;
-	kasan_free_pages(page, order);
+	kasan_free_pages(page, order, init);
 }
 
 /* Returns true if the struct page for the pfn is uninitialised */
@@ -456,12 +456,12 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 }
 #else
 static inline void kasan_free_nondeferred_pages(struct page *page, int order,
-							fpi_t fpi_flags)
+						bool init, fpi_t fpi_flags)
 {
 	if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
 			(fpi_flags & FPI_SKIP_KASAN_POISON))
 		return;
-	kasan_free_pages(page, order);
+	kasan_free_pages(page, order, init);
 }
 
 static inline bool early_page_uninitialised(unsigned long pfn)
@@ -1243,6 +1243,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
 			unsigned int order, bool check_free, fpi_t fpi_flags)
 {
 	int bad = 0;
+	bool init;
 
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
@@ -1300,16 +1301,21 @@ static __always_inline bool free_pages_prepare(struct page *page,
 		debug_check_no_obj_freed(page_address(page),
 					   PAGE_SIZE << order);
 	}
-	if (want_init_on_free())
-		kernel_init_free_pages(page, 1 << order);
 
 	kernel_poison_pages(page, 1 << order);
 
 	/*
+	 * As memory initialization might be integrated into KASAN,
+	 * kasan_free_pages and kernel_init_free_pages must be
+	 * kept together to avoid discrepancies in behavior.
+	 *
 	 * With hardware tag-based KASAN, memory tags must be set before the
 	 * page becomes unavailable via debug_pagealloc or arch_free_page.
 	 */
-	kasan_free_nondeferred_pages(page, order, fpi_flags);
+	init = want_init_on_free();
+	if (init && !kasan_has_integrated_init())
+		kernel_init_free_pages(page, 1 << order);
+	kasan_free_nondeferred_pages(page, order, init, fpi_flags);
 
 	/*
 	 * arch_free_page() can make the page's contents inaccessible.  s390
@@ -2316,17 +2322,32 @@ static bool check_new_pages(struct page *page, unsigned int order)
 inline void post_alloc_hook(struct page *page, unsigned int order,
 				gfp_t gfp_flags)
 {
+	bool init;
+
 	set_page_private(page, 0);
 	set_page_refcounted(page);
 
 	arch_alloc_page(page, order);
 	debug_pagealloc_map_pages(page, 1 << order);
-	kasan_alloc_pages(page, order);
+
+	/*
+	 * Page unpoisoning must happen before memory initialization.
+	 * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
+	 * allocations and the page unpoisoning code will complain.
+	 */
 	kernel_unpoison_pages(page, 1 << order);
-	set_page_owner(page, order, gfp_flags);
 
-	if (!want_init_on_free() && want_init_on_alloc(gfp_flags))
+	/*
+	 * As memory initialization might be integrated into KASAN,
+	 * kasan_alloc_pages and kernel_init_free_pages must be
+	 * kept together to avoid discrepancies in behavior.
+	 */
+	init = !want_init_on_free() && want_init_on_alloc(gfp_flags);
+	kasan_alloc_pages(page, order, init);
+	if (init && !kasan_has_integrated_init())
 		kernel_init_free_pages(page, 1 << order);
+
+	set_page_owner(page, order, gfp_flags);
 }
 
 static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,