[PATCH 6.2 070/110] maple_tree: fix a potential memory leak, OOB access, or other unpredictable bug

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From: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>

commit 1f5f12ece722aacea1769fb644f27790ede339dc upstream.

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@xxxxxxxxxxxxx
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 lib/maple_tree.c |   19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1298,26 +1298,21 @@ static inline void mas_alloc_nodes(struc
 	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;





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