Bluetooth: hci_bcsp: Fix memory leak in rx_skb

BugLink: https://bugs.launchpad.net/bugs/1840081

[ Upstream commit 4ce9146e ]

Syzkaller found that it is possible to provoke a memory leak by
never freeing rx_skb in struct bcsp_struct.

Fix by freeing in bcsp_close()
Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
Reported-by: syzbot+98162c885993b72f19c4@syzkaller.appspotmail.com
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/bluetooth/hci_bcsp.c

@@ -729,6 +729,11 @@ static int bcsp_close(struct hci_uart *hu)
 	skb_queue_purge(&bcsp->rel);
 	skb_queue_purge(&bcsp->unrel);
 
+	if (bcsp->rx_skb) {
+		kfree_skb(bcsp->rx_skb);
+		bcsp->rx_skb = NULL;
+	}
+
 	kfree(bcsp);
 	return 0;
 }