kasan: record and print the free track

Move free track from kasan_alloc_meta to kasan_free_meta in order to make
struct kasan_alloc_meta and kasan_free_meta size are both 16 bytes.  It is
a good size because it is the minimal redzone size and a good number of
alignment.

For free track, we make some modifications as shown below:
1) Remove the free_track from struct kasan_alloc_meta.
2) Add the free_track into struct kasan_free_meta.
3) Add a macro KASAN_KMALLOC_FREETRACK in order to check whether
   it can print free stack in KASAN report.

[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437

[walter-zh.wu@mediatek.com: build fix]
Link: http://lkml.kernel.org/r/20200710162440.23887-1-walter-zh.wu@mediatek.com
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Co-developed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Link: http://lkml.kernel.org/r/20200601051022.1230-1-walter-zh.wu@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index ad24666..f180677 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -50,7 +50,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags)
        return stack_depot_save(entries, nr_entries, flags);
 }
 
-static inline void set_track(struct kasan_track *track, gfp_t flags)
+void kasan_set_track(struct kasan_track *track, gfp_t flags)
 {
        track->pid = current->pid;
        track->stack = kasan_save_stack(flags);
@@ -298,24 +298,6 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
        return (void *)object + cache->kasan_info.free_meta_offset;
 }
 
-
-static void kasan_set_free_info(struct kmem_cache *cache,
-               void *object, u8 tag)
-{
-       struct kasan_alloc_meta *alloc_meta;
-       u8 idx = 0;
-
-       alloc_meta = get_alloc_info(cache, object);
-
-#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
-       idx = alloc_meta->free_track_idx;
-       alloc_meta->free_pointer_tag[idx] = tag;
-       alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
-#endif
-
-       set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
-}
-
 void kasan_poison_slab(struct page *page)
 {
        unsigned long i;
@@ -491,7 +473,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
                KASAN_KMALLOC_REDZONE);
 
        if (cache->flags & SLAB_KASAN)
-               set_track(&get_alloc_info(cache, object)->alloc_track, flags);
+               kasan_set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 
        return set_tag(object, tag);
 }

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d705863..248264b 100644 (file)
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -345,3 +345,25 @@ void kasan_record_aux_stack(void *addr)
        alloc_info->aux_stack[1] = alloc_info->aux_stack[0];
        alloc_info->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
 }
+
+void kasan_set_free_info(struct kmem_cache *cache,
+                               void *object, u8 tag)
+{
+       struct kasan_free_meta *free_meta;
+
+       free_meta = get_free_info(cache, object);
+       kasan_set_track(&free_meta->free_track, GFP_NOWAIT);
+
+       /*
+        *  the object was freed and has free track set
+        */
+       *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK;
+}
+
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+                               void *object, u8 tag)
+{
+       if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK)
+               return NULL;
+       return &get_free_info(cache, object)->free_track;
+}

diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index e200acb..a38c7a9 100644 (file)
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -80,6 +80,7 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info)
                break;
        case KASAN_FREE_PAGE:
        case KASAN_KMALLOC_FREE:
+       case KASAN_KMALLOC_FREETRACK:
                bug_type = "use-after-free";
                break;
        case KASAN_ALLOCA_LEFT:

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index f89a195..ac49945 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -17,15 +17,17 @@
 #define KASAN_PAGE_REDZONE      0xFE  /* redzone for kmalloc_large allocations */
 #define KASAN_KMALLOC_REDZONE   0xFC  /* redzone inside slub object */
 #define KASAN_KMALLOC_FREE      0xFB  /* object was freed (kmem_cache_free/kfree) */
+#define KASAN_KMALLOC_FREETRACK 0xFA  /* object was freed and has free track set */
 #else
 #define KASAN_FREE_PAGE         KASAN_TAG_INVALID
 #define KASAN_PAGE_REDZONE      KASAN_TAG_INVALID
 #define KASAN_KMALLOC_REDZONE   KASAN_TAG_INVALID
 #define KASAN_KMALLOC_FREE      KASAN_TAG_INVALID
+#define KASAN_KMALLOC_FREETRACK KASAN_TAG_INVALID
 #endif
 
-#define KASAN_GLOBAL_REDZONE    0xFA  /* redzone for global variable */
-#define KASAN_VMALLOC_INVALID   0xF9  /* unallocated space in vmapped page */
+#define KASAN_GLOBAL_REDZONE    0xF9  /* redzone for global variable */
+#define KASAN_VMALLOC_INVALID   0xF8  /* unallocated space in vmapped page */
 
 /*
  * Stack redzone shadow values
@@ -110,8 +112,9 @@ struct kasan_alloc_meta {
         * The free stack is stored into struct kasan_free_meta.
         */
        depot_stack_handle_t aux_stack[2];
-#endif
+#else
        struct kasan_track free_track[KASAN_NR_FREE_STACKS];
+#endif
 #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
        u8 free_pointer_tag[KASAN_NR_FREE_STACKS];
        u8 free_track_idx;
@@ -126,6 +129,9 @@ struct kasan_free_meta {
         * Otherwise it might be used for the allocator freelist.
         */
        struct qlist_node quarantine_link;
+#ifdef CONFIG_KASAN_GENERIC
+       struct kasan_track free_track;
+#endif
 };
 
 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
@@ -167,6 +173,10 @@ void kasan_report_invalid_free(void *object, unsigned long ip);
 struct page *kasan_addr_to_page(const void *addr);
 
 depot_stack_handle_t kasan_save_stack(gfp_t flags);
+void kasan_set_track(struct kasan_track *track, gfp_t flags);
+void kasan_set_free_info(struct kmem_cache *cache, void *object, u8 tag);
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+                               void *object, u8 tag);
 
 #if defined(CONFIG_KASAN_GENERIC) && \
        (defined(CONFIG_SLAB) || defined(CONFIG_SLUB))

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 978bc4a..4c53758 100644 (file)
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -145,6 +145,7 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
        if (IS_ENABLED(CONFIG_SLAB))
                local_irq_save(flags);
 
+       *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;
        ___cache_free(cache, object, _THIS_IP_);
 
        if (IS_ENABLED(CONFIG_SLAB))

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 445a9d5..4f49fa6 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -165,26 +165,6 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
                (void *)(object_addr + cache->object_size));
 }
 
-static struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
-               void *object, u8 tag)
-{
-       struct kasan_alloc_meta *alloc_meta;
-       int i = 0;
-
-       alloc_meta = get_alloc_info(cache, object);
-
-#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
-       for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
-               if (alloc_meta->free_pointer_tag[i] == tag)
-                       break;
-       }
-       if (i == KASAN_NR_FREE_STACKS)
-               i = alloc_meta->free_track_idx;
-#endif
-
-       return &alloc_meta->free_track[i];
-}
-
 static void describe_object(struct kmem_cache *cache, void *object,
                                const void *addr, u8 tag)
 {
@@ -196,8 +176,10 @@ static void describe_object(struct kmem_cache *cache, void *object,
                print_track(&alloc_info->alloc_track, "Allocated");
                pr_err("\n");
                free_track = kasan_get_free_track(cache, object, tag);
-               print_track(free_track, "Freed");
-               pr_err("\n");
+               if (free_track) {
+                       print_track(free_track, "Freed");
+                       pr_err("\n");
+               }
 
 #ifdef CONFIG_KASAN_GENERIC
                if (alloc_info->aux_stack[0]) {

diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 8a959fd..e02a36a 100644 (file)
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -161,3 +161,40 @@ void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size)
        kasan_poison_shadow((void *)addr, size, tag);
 }
 EXPORT_SYMBOL(__hwasan_tag_memory);
+
+void kasan_set_free_info(struct kmem_cache *cache,
+                               void *object, u8 tag)
+{
+       struct kasan_alloc_meta *alloc_meta;
+       u8 idx = 0;
+
+       alloc_meta = get_alloc_info(cache, object);
+
+#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
+       idx = alloc_meta->free_track_idx;
+       alloc_meta->free_pointer_tag[idx] = tag;
+       alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
+#endif
+
+       kasan_set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
+}
+
+struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
+                               void *object, u8 tag)
+{
+       struct kasan_alloc_meta *alloc_meta;
+       int i = 0;
+
+       alloc_meta = get_alloc_info(cache, object);
+
+#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
+       for (i = 0; i < KASAN_NR_FREE_STACKS; i++) {
+               if (alloc_meta->free_pointer_tag[i] == tag)
+                       break;
+       }
+       if (i == KASAN_NR_FREE_STACKS)
+               i = alloc_meta->free_track_idx;
+#endif
+
+       return &alloc_meta->free_track[i];
+}