ksmbd: request update to stale share config

ksmbd_share_config_get() retrieves the cached share config as long
as there is at least one connection to the share. This is an issue when
the user space utilities are used to update share configs. In that case
there is a need to inform ksmbd that it should not use the cached share
config for a new connection to the share. With these changes the tree
connection flag KSMBD_TREE_CONN_FLAG_UPDATE indicates this. When this
flag is set, ksmbd removes the share config from the shares hash table
meaning that ksmbd_share_config_get() ends up requesting a share config
from user space.

Signed-off-by: Atte Heikkilä <atteh.mailbox@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

ksmbd_netlink.h

@@ -349,6 +349,7 @@ enum KSMBD_TREE_CONN_STATUS {
 #define KSMBD_SHARE_FLAG_STREAMS		BIT(11)
 #define KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS	BIT(12)
 #define KSMBD_SHARE_FLAG_ACL_XATTR		BIT(13)
+#define KSMBD_SHARE_FLAG_UPDATE		BIT(14)
 
 /*
  * Tree connect request flags.
@@ -364,6 +365,7 @@ enum KSMBD_TREE_CONN_STATUS {
 #define KSMBD_TREE_CONN_FLAG_READ_ONLY		BIT(1)
 #define KSMBD_TREE_CONN_FLAG_WRITABLE		BIT(2)
 #define KSMBD_TREE_CONN_FLAG_ADMIN_ACCOUNT	BIT(3)
+#define KSMBD_TREE_CONN_FLAG_UPDATE		BIT(4)
 
 /*
  * RPC over IPC.

mgmt/share_config.c

@@ -51,12 +51,16 @@ static void kill_share(struct ksmbd_share_config *share)
 	kfree(share);
 }
 
-void __ksmbd_share_config_put(struct ksmbd_share_config *share)
+void ksmbd_share_config_del(struct ksmbd_share_config *share)
 {
 	down_write(&shares_table_lock);
 	hash_del(&share->hlist);
 	up_write(&shares_table_lock);
+}
 
+void __ksmbd_share_config_put(struct ksmbd_share_config *share)
+{
+	ksmbd_share_config_del(share);
 	kill_share(share);
 }
 

mgmt/share_config.h

@@ -64,6 +64,7 @@ static inline int test_share_config_flag(struct ksmbd_share_config *share,
 	return share->flags & flag;
 }
 
+void ksmbd_share_config_del(struct ksmbd_share_config *share);
 void __ksmbd_share_config_put(struct ksmbd_share_config *share);
 
 static inline void ksmbd_share_config_put(struct ksmbd_share_config *share)

mgmt/tree_connect.c

@@ -65,6 +65,20 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
 	}
 
 	tree_conn->flags = resp->connection_flags;
+	if (test_tree_conn_flag(tree_conn, KSMBD_TREE_CONN_FLAG_UPDATE)) {
+		struct ksmbd_share_config *new_sc;
+
+		ksmbd_share_config_del(sc);
+		new_sc = ksmbd_share_config_get(share_name);
+		if (!new_sc) {
+			pr_err("Failed to update stale share config\n");
+			status.ret = -ESTALE;
+			goto out_error;
+		}
+		ksmbd_share_config_put(sc);
+		sc = new_sc;
+	}
+
 	tree_conn->user = sess->user;
 	tree_conn->share_conf = sc;
 	status.tree_conn = tree_conn;

smb2pdu.c

@@ -1965,6 +1965,7 @@ int smb2_tree_connect(struct ksmbd_work *work)
 		rsp->hdr.Status = STATUS_SUCCESS;
 		rc = 0;
 		break;
+	case -ESTALE:
 	case -ENOENT:
 	case KSMBD_TREE_CONN_STATUS_NO_SHARE:
 		rsp->hdr.Status = STATUS_BAD_NETWORK_NAME;