[PATCH v2 1/2] maple_tree: Fix a potential memory leak, OOB access, or other unpredictable bug

[PATCH v2 1/2] maple_tree: Fix a potential memory leak, OOB access, or other unpredictable bug

[Peng Zhang]

In mas_alloc_nodes(), "node->node_count = 0" means to initialize the
node_count field of the new node, but the node may not be a new node.
It may be a node that existed before and node_count has a value, setting
it to 0 will cause a memory leak. At this time, mas->alloc->total will
be greater than the actual number of nodes in the linked list, which may
cause many other errors. For example, out-of-bounds access in mas_pop_node(),
and mas_pop_node() may return addresses that should not be used. Fix it
by initializing node_count only for new nodes.

Also, by the way, an if-else statement was removed to simplify the code.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org>
---
 lib/maple_tree.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index dd1a114d9e2b..938634bea2d6 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1303,26 +1303,21 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
 	node = mas->alloc;
 	node->request_count = 0;
 	while (requested) {
-		max_req = MAPLE_ALLOC_SLOTS;
-		if (node->node_count) {
-			unsigned int offset = node->node_count;
-
-			slots = (void **)&node->slot[offset];
-			max_req -= offset;
-		} else {
-			slots = (void **)&node->slot;
-		}
-
+		max_req = MAPLE_ALLOC_SLOTS - node->node_count;
+		slots = (void **)&node->slot[node->node_count];
 		max_req = min(requested, max_req);
 		count = mt_alloc_bulk(gfp, max_req, slots);
 		if (!count)
 			goto nomem_bulk;
 
+		if (node->node_count == 0) {
+			node->slot[0]->node_count = 0;
+			node->slot[0]->request_count = 0;
+		}
+
 		node->node_count += count;
 		allocated += count;
 		node = node->slot[0];
-		node->node_count = 0;
-		node->request_count = 0;
 		requested -= count;
 	}
 	mas->alloc->total = allocated;
-- 
2.20.1

[PATCH v2 2/2] maple_tree: Add a test case to check maple_alloc

[Peng Zhang]

Add a test case to check whether the number of maple_alloc structures is
actually equal to mas->alloc->total.

Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
---
 tools/testing/radix-tree/maple.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index 4c89ff333f6f..9286d3baa12d 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -55,6 +55,28 @@ struct rcu_reader_struct {
 	struct rcu_test_struct2 *test;
 };
 
+static int get_alloc_node_count(struct ma_state *mas)
+{
+	int count = 1;
+	struct maple_alloc *node = mas->alloc;
+
+	if (!node || ((unsigned long)node & 0x1))
+		return 0;
+	while (node->node_count) {
+		count += node->node_count;
+		node = node->slot[0];
+	}
+	return count;
+}
+
+static void check_mas_alloc_node_count(struct ma_state *mas)
+{
+	mas_node_count_gfp(mas, MAPLE_ALLOC_SLOTS + 1, GFP_KERNEL);
+	mas_node_count_gfp(mas, MAPLE_ALLOC_SLOTS + 3, GFP_KERNEL);
+	MT_BUG_ON(mas->tree, get_alloc_node_count(mas) != mas->alloc->total);
+	mas_destroy(mas);
+}
+
 /*
  * check_new_node() - Check the creation of new nodes and error path
  * verification.
@@ -69,6 +91,8 @@ static noinline void check_new_node(struct maple_tree *mt)
 
 	MA_STATE(mas, mt, 0, 0);
 
+	check_mas_alloc_node_count(&mas);
+
 	/* Try allocating 3 nodes */
 	mtree_lock(mt);
 	mt_set_non_kernel(0);
-- 
2.20.1

Re: [PATCH v2 1/2] maple_tree: Fix a potential memory leak, OOB access, or other unpredictable bug

[Liam R. Howlett]

* Peng Zhang <zhangpeng.00@bytedance.com> [230411 00:10]:
> In mas_alloc_nodes(), "node->node_count = 0" means to initialize the
> node_count field of the new node, but the node may not be a new node.
> It may be a node that existed before and node_count has a value, setting
> it to 0 will cause a memory leak. At this time, mas->alloc->total will
> be greater than the actual number of nodes in the linked list, which may
> cause many other errors. For example, out-of-bounds access in mas_pop_node(),
> and mas_pop_node() may return addresses that should not be used. Fix it
> by initializing node_count only for new nodes.
> 
> Also, by the way, an if-else statement was removed to simplify the code.
> 
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
> Cc: <stable@vger.kernel.org>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
>  lib/maple_tree.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index dd1a114d9e2b..938634bea2d6 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -1303,26 +1303,21 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
>  	node = mas->alloc;
>  	node->request_count = 0;
>  	while (requested) {
> -		max_req = MAPLE_ALLOC_SLOTS;
> -		if (node->node_count) {
> -			unsigned int offset = node->node_count;
> -
> -			slots = (void **)&node->slot[offset];
> -			max_req -= offset;
> -		} else {
> -			slots = (void **)&node->slot;
> -		}
> -
> +		max_req = MAPLE_ALLOC_SLOTS - node->node_count;
> +		slots = (void **)&node->slot[node->node_count];
>  		max_req = min(requested, max_req);
>  		count = mt_alloc_bulk(gfp, max_req, slots);
>  		if (!count)
>  			goto nomem_bulk;
>  
> +		if (node->node_count == 0) {
> +			node->slot[0]->node_count = 0;
> +			node->slot[0]->request_count = 0;
> +		}
> +
>  		node->node_count += count;
>  		allocated += count;
>  		node = node->slot[0];
> -		node->node_count = 0;
> -		node->request_count = 0;
>  		requested -= count;
>  	}
>  	mas->alloc->total = allocated;
> -- 
> 2.20.1
>