CVE-2026-74654 serial: 8250_dma: Clear stale RX state on shutdown

In the Linux kernel, the following vulnerability has been resolved: serial: 8250dma: Clear stale RX state on shutdown serial8250releasedma terminates RX DMA and releases the channel, but leaves rxrunning set. If the port is closed while an RX transfer is active, the stale state remains while rxch...