mm, kasan: SLAB support

Add KASAN hooks to SLAB allocator.

This patch is based on the "mm: kasan: unified support for SLUB and SLAB
allocators" patch originally prepared by Dmitry Chernenkov.

Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Konstantin Serebryany <kcc@google.com>
Cc: Dmitry Chernenkov <dmitryc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 179 insertions, 11 deletions

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 1ad20ade8c91..7c82509ef169 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -334,6 +334,59 @@ void kasan_free_pages(struct page *page, unsigned int order)
                                 KASAN_FREE_PAGE);
 }
 
+#ifdef CONFIG_SLAB
+/*
+ * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
+ * For larger allocations larger redzones are used.
+ */
+static size_t optimal_redzone(size_t object_size)
+{
+        int rz =
+                object_size <= 64        - 16   ? 16 :
+                object_size <= 128       - 32   ? 32 :
+                object_size <= 512       - 64   ? 64 :
+                object_size <= 4096      - 128  ? 128 :
+                object_size <= (1 << 14) - 256  ? 256 :
+                object_size <= (1 << 15) - 512  ? 512 :
+                object_size <= (1 << 16) - 1024 ? 1024 : 2048;
+        return rz;
+}
+
+void kasan_cache_create(struct kmem_cache *cache, size_t *size,
+                        unsigned long *flags)
+{
+        int redzone_adjust;
+        /* Make sure the adjusted size is still less than
+         * KMALLOC_MAX_CACHE_SIZE.
+         * TODO: this check is only useful for SLAB, but not SLUB. We'll need
+         * to skip it for SLUB when it starts using kasan_cache_create().
+         */
+        if (*size > KMALLOC_MAX_CACHE_SIZE -
+            sizeof(struct kasan_alloc_meta) -
+            sizeof(struct kasan_free_meta))
+                return;
+        *flags |= SLAB_KASAN;
+        /* Add alloc meta. */
+        cache->kasan_info.alloc_meta_offset = *size;
+        *size += sizeof(struct kasan_alloc_meta);
+
+        /* Add free meta. */
+        if (cache->flags & SLAB_DESTROY_BY_RCU || cache->ctor ||
+            cache->object_size < sizeof(struct kasan_free_meta)) {
+                cache->kasan_info.free_meta_offset = *size;
+                *size += sizeof(struct kasan_free_meta);
+        }
+        redzone_adjust = optimal_redzone(cache->object_size) -
+                (*size - cache->object_size);
+        if (redzone_adjust > 0)
+                *size += redzone_adjust;
+        *size = min(KMALLOC_MAX_CACHE_SIZE,
+                    max(*size,
+                        cache->object_size +
+                        optimal_redzone(cache->object_size)));
+}
+#endif
+
 void kasan_poison_slab(struct page *page)
 {
         kasan_poison_shadow(page_address(page),
@@ -351,8 +404,36 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
         kasan_poison_shadow(object,
                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
                         KASAN_KMALLOC_REDZONE);
+#ifdef CONFIG_SLAB
+        if (cache->flags & SLAB_KASAN) {
+                struct kasan_alloc_meta *alloc_info =
+                        get_alloc_info(cache, object);
+                alloc_info->state = KASAN_STATE_INIT;
+        }
+#endif
+}
+
+static inline void set_track(struct kasan_track *track)
+{
+        track->cpu = raw_smp_processor_id();
+        track->pid = current->pid;
+        track->when = jiffies;
 }
 
+#ifdef CONFIG_SLAB
+struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
+                                        const void *object)
+{
+        return (void *)object + cache->kasan_info.alloc_meta_offset;
+}
+
+struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
+                                      const void *object)
+{
+        return (void *)object + cache->kasan_info.free_meta_offset;
+}
+#endif
+
 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 {
         kasan_kmalloc(cache, object, cache->object_size);
@@ -367,6 +448,17 @@ void kasan_slab_free(struct kmem_cache *cache, void *object)
         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
                 return;
 
+#ifdef CONFIG_SLAB
+        if (cache->flags & SLAB_KASAN) {
+                struct kasan_free_meta *free_info =
+                        get_free_info(cache, object);
+                struct kasan_alloc_meta *alloc_info =
+                        get_alloc_info(cache, object);
+                alloc_info->state = KASAN_STATE_FREE;
+                set_track(&free_info->track);
+        }
+#endif
+
         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 }
 
@@ -386,6 +478,16 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
         kasan_unpoison_shadow(object, size);
         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
                 KASAN_KMALLOC_REDZONE);
+#ifdef CONFIG_SLAB
+        if (cache->flags & SLAB_KASAN) {
+                struct kasan_alloc_meta *alloc_info =
+                        get_alloc_info(cache, object);
+
+                alloc_info->state = KASAN_STATE_ALLOC;
+                alloc_info->alloc_size = size;
+                set_track(&alloc_info->track);
+        }
+#endif
 }
 EXPORT_SYMBOL(kasan_kmalloc);
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 4f6c62e5c21e..7b9e4ab9b66b 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -54,6 +54,40 @@ struct kasan_global {
 #endif
 };
 
+/**
+ * Structures to keep alloc and free tracks *
+ */
+
+enum kasan_state {
+        KASAN_STATE_INIT,
+        KASAN_STATE_ALLOC,
+        KASAN_STATE_FREE
+};
+
+struct kasan_track {
+        u64 cpu : 6;                    /* for NR_CPUS = 64 */
+        u64 pid : 16;                   /* 65536 processes */
+        u64 when : 42;                  /* ~140 years */
+};
+
+struct kasan_alloc_meta {
+        u32 state : 2;  /* enum kasan_state */
+        u32 alloc_size : 30;
+        struct kasan_track track;
+};
+
+struct kasan_free_meta {
+        /* Allocator freelist pointer, unused by KASAN. */
+        void **freelist;
+        struct kasan_track track;
+};
+
+struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
+                                        const void *object);
+struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
+                                        const void *object);
+
+
 static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 {
         return (void *)(((unsigned long)shadow_addr - KASAN_SHADOW_OFFSET)
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 745aa8f36028..3e3385cc97ac 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -115,6 +115,46 @@ static inline bool init_task_stack_addr(const void *addr)
                         sizeof(init_thread_union.stack));
 }
 
+#ifdef CONFIG_SLAB
+static void print_track(struct kasan_track *track)
+{
+        pr_err("PID = %u, CPU = %u, timestamp = %lu\n", track->pid,
+               track->cpu, (unsigned long)track->when);
+}
+
+static void object_err(struct kmem_cache *cache, struct page *page,
+                        void *object, char *unused_reason)
+{
+        struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
+        struct kasan_free_meta *free_info;
+
+        dump_stack();
+        pr_err("Object at %p, in cache %s\n", object, cache->name);
+        if (!(cache->flags & SLAB_KASAN))
+                return;
+        switch (alloc_info->state) {
+        case KASAN_STATE_INIT:
+                pr_err("Object not allocated yet\n");
+                break;
+        case KASAN_STATE_ALLOC:
+                pr_err("Object allocated with size %u bytes.\n",
+                       alloc_info->alloc_size);
+                pr_err("Allocation:\n");
+                print_track(&alloc_info->track);
+                break;
+        case KASAN_STATE_FREE:
+                pr_err("Object freed, allocated with size %u bytes\n",
+                       alloc_info->alloc_size);
+                free_info = get_free_info(cache, object);
+                pr_err("Allocation:\n");
+                print_track(&alloc_info->track);
+                pr_err("Deallocation:\n");
+                print_track(&free_info->track);
+                break;
+        }
+}
+#endif
+
 static void print_address_description(struct kasan_access_info *info)
 {
         const void *addr = info->access_addr;
@@ -126,17 +166,10 @@ static void print_address_description(struct kasan_access_info *info)
                 if (PageSlab(page)) {
                         void *object;
                         struct kmem_cache *cache = page->slab_cache;
-                        void *last_object;
-
-                        object = virt_to_obj(cache, page_address(page), addr);
-                        last_object = page_address(page) +
-                                page->objects * cache->size;
-
-                        if (unlikely(object > last_object))
-                                object = last_object; /* we hit into padding */
-
+                        object = nearest_obj(cache, page,
+                                                (void *)info->access_addr);
                         object_err(cache, page, object,
-                                "kasan: bad access detected");
+                                        "kasan: bad access detected");
                         return;
                 }
                 dump_page(page, "kasan: bad access detected");
@@ -146,7 +179,6 @@ static void print_address_description(struct kasan_access_info *info)
                 if (!init_task_stack_addr(addr))
                         pr_err("Address belongs to variable %pS\n", addr);
         }
-
         dump_stack();
 }