Commit 0a2b18d9 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

maple_tree: add smp_rmb() to dead node detection 

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: 54a611b6 ("Maple Tree: add new data structure")
Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c13af03d

lib/maple_tree.c

+6 −2
Original line number Diff line number Diff line
@@ -539,9 +539,11 @@ 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);

}
@@ -556,6 +558,8 @@ 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);

}