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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: 54a611b605 ("Maple Tree: add new data structure")
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peng Zhang 2023-04-11 12:10:04 +08:00 committed by Andrew Morton
parent 9235756885
commit 1f5f12ece7
1 changed files with 7 additions and 12 deletions
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19
lib/maple_tree.c
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@ -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;