[PATCH] ocfs2: fix race between ocfs2_control_install_private() and ocfs2_control_release()

[Joseph Qi]

Move atomic_inc(&ocfs2_control_opened) and the handshake state update
inside ocfs2_control_lock to close a race window where
ocfs2_control_release() can observe ocfs2_control_opened dropping to
zero (resetting ocfs2_control_this_node and running_proto) while
ocfs2_control_install_private() is about to bump the counter and mark
the connection valid.

Fixes: 3cfd4ab6b6b4 ("ocfs2: Add the local node id to the handshake.")
Reported-by: Ginger <ginger@xxxxxxxxx>
Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
---
 fs/ocfs2/stack_user.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
index 5803f1dee679..91e19d33847c 100644
--- a/fs/ocfs2/stack_user.c
+++ b/fs/ocfs2/stack_user.c
@@ -327,18 +327,14 @@ static int ocfs2_control_install_private(struct file *file)
 		ocfs2_control_this_node = p->op_this_node;
 		running_proto.pv_major = p->op_proto.pv_major;
 		running_proto.pv_minor = p->op_proto.pv_minor;
-	}
-
-out_unlock:
-	mutex_unlock(&ocfs2_control_lock);
-
-	if (!rc && set_p) {
-		/* We set the global values successfully */
 		atomic_inc(&ocfs2_control_opened);
 		ocfs2_control_set_handshake_state(file,
 					OCFS2_CONTROL_HANDSHAKE_VALID);
 	}
 
+out_unlock:
+	mutex_unlock(&ocfs2_control_lock);
+
 	return rc;
 }
 
-- 
2.39.3