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...

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