maple_tree: fix potential rcu issue

Ensure the node isn't dead after reading the node end.

Link: https://lkml.kernel.org/r/20230120162650.984577-3-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 1c5d3b640a2469d06818362f431c67859304577e..7e3cf5b7e68b34e7d77c8cd3a0722941fcea6b1a 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4655,13 +4655,13 @@ static inline void *mas_next_nentry(struct ma_state *mas,
        pivots = ma_pivots(node, type);
        slots = ma_slots(node, type);
        mas->index = mas_safe_min(mas, pivots, mas->offset);
+       count = ma_data_end(node, type, pivots, mas->max);
        if (ma_dead_node(node))
                return NULL;
 
        if (mas->index > max)
                return NULL;
 
-       count = ma_data_end(node, type, pivots, mas->max);
        if (mas->offset > count)
                return NULL;