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-rw-r--r--mm/slub.c45
1 files changed, 30 insertions, 15 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 9bf44955c4f1..b762450fc9f0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -551,15 +551,32 @@ static void print_section(char *level, char *text, u8 *addr,
metadata_access_disable();
}
+/*
+ * See comment in calculate_sizes().
+ */
+static inline bool freeptr_outside_object(struct kmem_cache *s)
+{
+ return s->offset >= s->inuse;
+}
+
+/*
+ * Return offset of the end of info block which is inuse + free pointer if
+ * not overlapping with object.
+ */
+static inline unsigned int get_info_end(struct kmem_cache *s)
+{
+ if (freeptr_outside_object(s))
+ return s->inuse + sizeof(void *);
+ else
+ return s->inuse;
+}
+
static struct track *get_track(struct kmem_cache *s, void *object,
enum track_item alloc)
{
struct track *p;
- if (s->offset)
- p = object + s->offset + sizeof(void *);
- else
- p = object + s->inuse;
+ p = object + get_info_end(s);
return p + alloc;
}
@@ -686,10 +703,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
print_section(KERN_ERR, "Redzone ", p + s->object_size,
s->inuse - s->object_size);
- if (s->offset)
- off = s->offset + sizeof(void *);
- else
- off = s->inuse;
+ off = get_info_end(s);
if (s->flags & SLAB_STORE_USER)
off += 2 * sizeof(struct track);
@@ -782,7 +796,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
* object address
* Bytes of the object to be managed.
* If the freepointer may overlay the object then the free
- * pointer is the first word of the object.
+ * pointer is at the middle of the object.
*
* Poisoning uses 0x6b (POISON_FREE) and the last byte is
* 0xa5 (POISON_END)
@@ -816,11 +830,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
{
- unsigned long off = s->inuse; /* The end of info */
-
- if (s->offset)
- /* Freepointer is placed after the object. */
- off += sizeof(void *);
+ unsigned long off = get_info_end(s); /* The end of info */
if (s->flags & SLAB_STORE_USER)
/* We also have user information there */
@@ -907,7 +917,7 @@ static int check_object(struct kmem_cache *s, struct page *page,
check_pad_bytes(s, page, p);
}
- if (!s->offset && val == SLUB_RED_ACTIVE)
+ if (!freeptr_outside_object(s) && val == SLUB_RED_ACTIVE)
/*
* Object and freepointer overlap. Cannot check
* freepointer while object is allocated.
@@ -3587,6 +3597,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
*
* This is the case if we do RCU, have a constructor or
* destructor or are poisoning the objects.
+ *
+ * The assumption that s->offset >= s->inuse means free
+ * pointer is outside of the object is used in the
+ * freeptr_outside_object() function. If that is no
+ * longer true, the function needs to be modified.
*/
s->offset = size;
size += sizeof(void *);