+ maple_tree-fix-a-potential-memory-leak-oob-access-or-other-unpredictable-bug.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: maple_tree: fix a potential memory leak, OOB access, or other unpredictable bug
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     maple_tree-fix-a-potential-memory-leak-oob-access-or-other-unpredictable-bug.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-fix-a-potential-memory-leak-oob-access-or-other-unpredictable-bug.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Peng Zhang <zhangpeng.00@bytedance.com>
Subject: maple_tree: fix a potential memory leak, OOB access, or other unpredictable bug
Date: Tue, 11 Apr 2023 12:10:04 +0800

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: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/maple_tree.c |   19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

--- a/lib/maple_tree.c~maple_tree-fix-a-potential-memory-leak-oob-access-or-other-unpredictable-bug
+++ a/lib/maple_tree.c
@@ -1303,26 +1303,21 @@ 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;
_

Patches currently in -mm which might be from zhangpeng.00@bytedance.com are

maple_tree-fix-a-potential-memory-leak-oob-access-or-other-unpredictable-bug.patch
mm-kfence-improve-the-performance-of-__kfence_alloc-and-__kfence_free.patch
maple_tree-simplify-mas_wr_node_walk.patch
maple_tree-use-correct-variable-type-in-sizeof.patch