| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.12 055/133] tty/serial: at91: Handle shutdown more safely | Date | Tue, 4 Feb 2014 13:07:36 -0800 |
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3.12-stable review patch. If anyone has any objections, please let me know.
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From: Marek Roszko <mark.roszko@gmail.com>
commit 0cc7c6c7916b1b6f34350ff1473b80b9f7e459c0 upstream.
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:
[<c02092b0>] (atmel_tasklet_func+0x514/0x814) from [<c001fd34>] (tasklet_action+0x70/0xa8) [<c001fd34>] (tasklet_action+0x70/0xa8) from [<c001f60c>] (__do_softirq+0x90/0x144) [<c001f60c>] (__do_softirq+0x90/0x144) from [<c001fa18>] (irq_exit+0x40/0x4c) [<c001fa18>] (irq_exit+0x40/0x4c) from [<c000e298>] (handle_IRQ+0x64/0x84) [<c000e298>] (handle_IRQ+0x64/0x84) from [<c000d6c0>] (__irq_svc+0x40/0x50) [<c000d6c0>] (__irq_svc+0x40/0x50) from [<c0208060>] (atmel_rx_dma_release+0x88/0xb8) [<c0208060>] (atmel_rx_dma_release+0x88/0xb8) from [<c0209740>] (atmel_shutdown+0x104/0x160) [<c0209740>] (atmel_shutdown+0x104/0x160) from [<c0205e8c>] (uart_port_shutdown+0x2c/0x38)
Signed-off-by: Marek Roszko <mark.roszko@gmail.com> Acked-by: Leilei Zhao <leilei.zhao@atmel.com> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/tty/serial/atmel_serial.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
--- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -1633,12 +1633,24 @@ static int atmel_startup(struct uart_por static void atmel_shutdown(struct uart_port *port) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); + + /* + * Clear out any scheduled tasklets before + * we destroy the buffers + */ + tasklet_kill(&atmel_port->tasklet); + /* - * Ensure everything is stopped. + * 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. */ @@ -1648,12 +1660,6 @@ static void atmel_shutdown(struct uart_p 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 */ free_irq(port->irq, port);
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