Commit 1f5f12ec authored by Peng Zhang's avatar Peng Zhang Committed by Andrew Morton
Browse files

maple_tree: fix a potential memory leak, OOB access, or other unpredictable bug 

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.

Link: https://lkml.kernel.org/r/20230411041005.26205-1-zhangpeng.00@bytedance.com


Fixes: 54a611b6 ("Maple Tree: add new data structure")
Signed-off-by: default avatarPeng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 92357568

lib/maple_tree.c

+7 −12
Original line number Diff line number Diff line
@@ -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;