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>

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 9f5faef..30aa2be 100644 (file)
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -96,6 +96,11 @@ static __always_inline bool kasan_enabled(void)
        return static_branch_likely(&kasan_flag_enabled);
 }
 
+static inline bool kasan_has_integrated_init(void)
+{
+       return kasan_enabled();
+}
+
 #else /* CONFIG_KASAN_HW_TAGS */
 
 static inline bool kasan_enabled(void)
@@ -103,6 +108,11 @@ static inline bool kasan_enabled(void)
        return true;
 }
 
+static inline bool kasan_has_integrated_init(void)
+{
+       return false;
+}
+
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 slab_flags_t __kasan_never_merge(void);
@@ -120,20 +130,20 @@ static __always_inline void kasan_unpoison_range(const void *addr, size_t size)
                __kasan_unpoison_range(addr, size);
 }
 
-void __kasan_alloc_pages(struct page *page, unsigned int order);
+void __kasan_alloc_pages(struct page *page, unsigned int order, bool init);
 static __always_inline void kasan_alloc_pages(struct page *page,
-                                               unsigned int order)
+                                               unsigned int order, bool init)
 {
        if (kasan_enabled())
-               __kasan_alloc_pages(page, order);
+               __kasan_alloc_pages(page, order, init);
 }
 
-void __kasan_free_pages(struct page *page, unsigned int order);
+void __kasan_free_pages(struct page *page, unsigned int order, bool init);
 static __always_inline void kasan_free_pages(struct page *page,
-                                               unsigned int order)
+                                               unsigned int order, bool init)
 {
        if (kasan_enabled())
-               __kasan_free_pages(page, order);
+               __kasan_free_pages(page, order, init);
 }
 
 void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
@@ -277,13 +287,17 @@ static inline bool kasan_enabled(void)
 {
        return false;
 }
+static inline bool kasan_has_integrated_init(void)
+{
+       return false;
+}
 static inline slab_flags_t kasan_never_merge(void)
 {
        return 0;
 }
 static inline void kasan_unpoison_range(const void *address, size_t size) {}
-static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
-static inline void kasan_free_pages(struct page *page, unsigned int order) {}
+static inline void kasan_alloc_pages(struct page *page, unsigned int order, bool init) {}
+static inline void kasan_free_pages(struct page *page, unsigned int order, bool init) {}
 static inline void kasan_cache_create(struct kmem_cache *cache,
                                      unsigned int *size,
                                      slab_flags_t *flags) {}

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index b3d8eb1..efe58e5 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -97,7 +97,7 @@ slab_flags_t __kasan_never_merge(void)
        return 0;
 }
 
-void __kasan_alloc_pages(struct page *page, unsigned int order)
+void __kasan_alloc_pages(struct page *page, unsigned int order, bool init)
 {
        u8 tag;
        unsigned long i;
@@ -108,14 +108,14 @@ void __kasan_alloc_pages(struct page *page, unsigned int order)
        tag = kasan_random_tag();
        for (i = 0; i < (1 << order); i++)
                page_kasan_tag_set(page + i, tag);
-       kasan_unpoison(page_address(page), PAGE_SIZE << order, false);
+       kasan_unpoison(page_address(page), PAGE_SIZE << order, init);
 }
 
-void __kasan_free_pages(struct page *page, unsigned int order)
+void __kasan_free_pages(struct page *page, unsigned int order, bool init)
 {
        if (likely(!PageHighMem(page)))
                kasan_poison(page_address(page), PAGE_SIZE << order,
-                            KASAN_FREE_PAGE, false);
+                            KASAN_FREE_PAGE, init);
 }
 
 /*

diff --git a/mm/mempool.c b/mm/mempool.c
index 79959fa..fe19d29 100644 (file)
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -106,7 +106,7 @@ static __always_inline void kasan_poison_element(mempool_t *pool, void *element)
        if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
                kasan_slab_free_mempool(element);
        else if (pool->alloc == mempool_alloc_pages)
-               kasan_free_pages(element, (unsigned long)pool->pool_data);
+               kasan_free_pages(element, (unsigned long)pool->pool_data, false);
 }
 
 static void kasan_unpoison_element(mempool_t *pool, void *element)
@@ -114,7 +114,7 @@ static void kasan_unpoison_element(mempool_t *pool, void *element)
        if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
                kasan_unpoison_range(element, __ksize(element));
        else if (pool->alloc == mempool_alloc_pages)
-               kasan_alloc_pages(element, (unsigned long)pool->pool_data);
+               kasan_alloc_pages(element, (unsigned long)pool->pool_data, false);
 }
 
 static __always_inline void add_element(mempool_t *pool, void *element)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 342cabf..6314de5 100644 (file)
--- 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,