maple_tree: add smp_rmb() to dead node detection

commit 0a2b18d948838e16912b3b627b504ab062b7d02a upstream.

Add an smp_rmb() before reading the parent pointer to ensure that anything
read from the node prior to the parent pointer hasn't been reordered ahead
of this check.

The is necessary for RCU mode.

Link: https://lkml.kernel.org/r/20230227173632.3292573-7-surenb@google.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Cc: stable@vger.kernel.org
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index aeb218f2ef285c915e7269b7dece0f616e18e8ed..1ec87280946bb01e369f5c12465c9f6c76448879 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -534,9 +534,11 @@ static inline struct maple_node *mte_parent(const struct maple_enode *enode)
  */
 static inline bool ma_dead_node(const struct maple_node *node)
 {
-       struct maple_node *parent = (void *)((unsigned long)
-                                            node->parent & ~MAPLE_NODE_MASK);
+       struct maple_node *parent;
 
+       /* Do not reorder reads from the node prior to the parent check */
+       smp_rmb();
+       parent = (void *)((unsigned long) node->parent & ~MAPLE_NODE_MASK);
        return (parent == node);
 }
 
@@ -551,6 +553,8 @@ static inline bool mte_dead_node(const struct maple_enode *enode)
        struct maple_node *parent, *node;
 
        node = mte_to_node(enode);
+       /* Do not reorder reads from the node prior to the parent check */
+       smp_rmb();
        parent = mte_parent(enode);
        return (parent == node);
 }