The patch titled
Subject: mm: kmemleak: fix delete_object_*() race when called on the same memory block
has been removed from the -mm tree. Its filename was
mm-kmemleak-fix-delete_object_-race-when-called-on-the-same-memory-block.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Catalin Marinas <catalin.marinas@xxxxxxx>
Subject: mm: kmemleak: fix delete_object_*() race when called on the same memory block
Calling delete_object_*() on the same pointer is not a standard use case
(unless there is a bug in the code calling kmemleak_free()). However,
during kmemleak disabling (error or user triggered via /sys), there is a
potential race between kmemleak_free() calls on a CPU and
__kmemleak_do_cleanup() on a different CPU. The current delete_object_*()
implementation first performs a look-up holding kmemleak_lock, increments
the object->use_count and then re-acquires kmemleak_lock to remove the
object from object_tree_root and object_list.
This patch simplifies the delete_object_*() mechanism to both look up and
remove an object from the object_tree_root and object_list atomically
(guarded by kmemleak_lock). This allows safe concurrent calls to
delete_object_*() on the same pointer without additional locking for
synchronising the kmemleak_free_enabled flag.
A side effect is a slight improvement in the delete_object_*() performance
by avoiding acquiring kmemleak_lock twice and incrementing/decrementing
object->use_count.
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kmemleak.c | 39 ++++++++++++++++++++++++++-------------
1 file changed, 26 insertions(+), 13 deletions(-)
diff -puN mm/kmemleak.c~mm-kmemleak-fix-delete_object_-race-when-called-on-the-same-memory-block mm/kmemleak.c
--- a/mm/kmemleak.c~mm-kmemleak-fix-delete_object_-race-when-called-on-the-same-memory-block
+++ a/mm/kmemleak.c
@@ -498,6 +498,27 @@ static struct kmemleak_object *find_and_
}
/*
+ * Look up an object in the object search tree and remove it from both
+ * object_tree_root and object_list. The returned object's use_count should be
+ * at least 1, as initially set by create_object().
+ */
+static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias)
+{
+ unsigned long flags;
+ struct kmemleak_object *object;
+
+ write_lock_irqsave(&kmemleak_lock, flags);
+ object = lookup_object(ptr, alias);
+ if (object) {
+ rb_erase(&object->rb_node, &object_tree_root);
+ list_del_rcu(&object->object_list);
+ }
+ write_unlock_irqrestore(&kmemleak_lock, flags);
+
+ return object;
+}
+
+/*
* Save stack trace to the given array of MAX_TRACE size.
*/
static int __save_stack_trace(unsigned long *trace)
@@ -600,20 +621,14 @@ out:
}
/*
- * Remove the metadata (struct kmemleak_object) for a memory block from the
- * object_list and object_tree_root and decrement its use_count.
+ * Mark the object as not allocated and schedule RCU freeing via put_object().
*/
static void __delete_object(struct kmemleak_object *object)
{
unsigned long flags;
- write_lock_irqsave(&kmemleak_lock, flags);
- rb_erase(&object->rb_node, &object_tree_root);
- list_del_rcu(&object->object_list);
- write_unlock_irqrestore(&kmemleak_lock, flags);
-
WARN_ON(!(object->flags & OBJECT_ALLOCATED));
- WARN_ON(atomic_read(&object->use_count) < 2);
+ WARN_ON(atomic_read(&object->use_count) < 1);
/*
* Locking here also ensures that the corresponding memory block
@@ -633,7 +648,7 @@ static void delete_object_full(unsigned
{
struct kmemleak_object *object;
- object = find_and_get_object(ptr, 0);
+ object = find_and_remove_object(ptr, 0);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Freeing unknown object at 0x%08lx\n",
@@ -642,7 +657,6 @@ static void delete_object_full(unsigned
return;
}
__delete_object(object);
- put_object(object);
}
/*
@@ -655,7 +669,7 @@ static void delete_object_part(unsigned
struct kmemleak_object *object;
unsigned long start, end;
- object = find_and_get_object(ptr, 1);
+ object = find_and_remove_object(ptr, 1);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx "
@@ -663,7 +677,6 @@ static void delete_object_part(unsigned
#endif
return;
}
- __delete_object(object);
/*
* Create one or two objects that may result from the memory block
@@ -681,7 +694,7 @@ static void delete_object_part(unsigned
create_object(ptr + size, end - ptr - size, object->min_count,
GFP_KERNEL);
- put_object(object);
+ __delete_object(object);
}
static void __paint_it(struct kmemleak_object *object, int color)
_
Patches currently in -mm which might be from catalin.marinas@xxxxxxx are
origin.patch
linux-next.patch
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