From: Catalin Marinas <catalin.marinas@arm.com>
Date: Fri, 4 Oct 2019 14:46:24 +0100
Subject: kmemleak: Do not corrupt the object_list during clean-up
Patch-mainline: v5.4-rc4
Git-commit: 2abd839aa7e615f2bbc50c8ba7deb9e40d186768
References: bsc#1162702

In case of an error (e.g. memory pool too small), kmemleak disables
itself and cleans up the already allocated metadata objects. However, if
this happens early before the RCU callback mechanism is available,
put_object() skips call_rcu() and frees the object directly. This is not
safe with the RCU list traversal in __kmemleak_do_cleanup().

Change the list traversal in __kmemleak_do_cleanup() to
list_for_each_entry_safe() and remove the rcu_read_{lock,unlock} since
the kmemleak is already disabled at this point. In addition, avoid an
unnecessary metadata object rb-tree look-up since it already has the
struct kmemleak_object pointer.

Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reported-by: Marc Dionne <marc.c.dionne@gmail.com>
Reported-by: Ted Ts'o <tytso@mit.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 mm/kmemleak.c |   30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -527,6 +527,16 @@ static struct kmemleak_object *find_and_
 }
 
 /*
+ * Remove an object from the object_tree_root and object_list. Must be called
+ * with the kmemleak_lock held _if_ kmemleak is still enabled.
+ */
+static void __remove_object(struct kmemleak_object *object)
+{
+	rb_erase(&object->rb_node, &object_tree_root);
+	list_del_rcu(&object->object_list);
+}
+
+/*
  * 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().
@@ -538,10 +548,8 @@ static struct kmemleak_object *find_and_
 
 	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);
-	}
+	if (object)
+		__remove_object(object);
 	write_unlock_irqrestore(&kmemleak_lock, flags);
 
 	return object;
@@ -1834,12 +1842,16 @@ static const struct file_operations kmem
 
 static void __kmemleak_do_cleanup(void)
 {
-	struct kmemleak_object *object;
+	struct kmemleak_object *object, *tmp;
 
-	rcu_read_lock();
-	list_for_each_entry_rcu(object, &object_list, object_list)
-		delete_object_full(object->pointer);
-	rcu_read_unlock();
+	/*
+	 * Kmemleak has already been disabled, no need for RCU list traversal
+	 * or kmemleak_lock held.
+	 */
+	list_for_each_entry_safe(object, tmp, &object_list, object_list) {
+		__remove_object(object);
+		__delete_object(object);
+	}
 }
 
 /*