From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> 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@xxxxxxxxxx Fixes: 54a611b60590 ("Maple Tree: add new data structure") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- lib/maple_tree.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -534,9 +534,11 @@ static inline struct maple_node *mte_par */ 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 s 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); }
