From 0cc7c6c7916b1b6f34350ff1473b80b9f7e459c0 Mon Sep 17 00:00:00 2001 From: Marek Roszko Date: Tue, 7 Jan 2014 11:45:06 +0100 Subject: [PATCH] tty/serial: at91: Handle shutdown more safely Interrupts were being cleaned up late in the shutdown handler, it is possible that an interrupt can occur and schedule a tasklet that runs after the port is cleaned up. There is a null dereference due to this race condition with the following stacktrace: [] (atmel_tasklet_func+0x514/0x814) from [] (tasklet_action+0x70/0xa8) [] (tasklet_action+0x70/0xa8) from [] (__do_softirq+0x90/0x144) [] (__do_softirq+0x90/0x144) from [] (irq_exit+0x40/0x4c) [] (irq_exit+0x40/0x4c) from [] (handle_IRQ+0x64/0x84) [] (handle_IRQ+0x64/0x84) from [] (__irq_svc+0x40/0x50) [] (__irq_svc+0x40/0x50) from [] (atmel_rx_dma_release+0x88/0xb8) [] (atmel_rx_dma_release+0x88/0xb8) from [] (atmel_shutdown+0x104/0x160) [] (atmel_shutdown+0x104/0x160) from [] (uart_port_shutdown+0x2c/0x38) Signed-off-by: Marek Roszko Acked-by: Leilei Zhao Cc: # v3.12 Signed-off-by: Nicolas Ferre Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/atmel_serial.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index c7d99af46a96..48ea47a32d5f 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -1650,12 +1650,24 @@ static int atmel_startup(struct uart_port *port) static void atmel_shutdown(struct uart_port *port) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); + /* - * Ensure everything is stopped. + * Clear out any scheduled tasklets before + * we destroy the buffers + */ + tasklet_kill(&atmel_port->tasklet); + + /* + * Ensure everything is stopped and + * disable all interrupts, port and break condition. */ atmel_stop_rx(port); atmel_stop_tx(port); + UART_PUT_CR(port, ATMEL_US_RSTSTA); + UART_PUT_IDR(port, -1); + + /* * Shut-down the DMA. */ @@ -1664,12 +1676,6 @@ static void atmel_shutdown(struct uart_port *port) if (atmel_port->release_tx) atmel_port->release_tx(port); - /* - * Disable all interrupts, port and break condition. - */ - UART_PUT_CR(port, ATMEL_US_RSTSTA); - UART_PUT_IDR(port, -1); - /* * Free the interrupt */ -- 2.34.1