From: Marek Roszko <mark.roszko@xxxxxxxxx>
The uart timer will schedule a tasklet when it fires. It is possible that it
can fire inside _shutdown before it is killed in the dma and pdc cleanup
routines. This causes a tasklet that exists after the port is shutdown, so when
the kernel finally executes it, it panics as the tty port is NULL.
This is a somewhat rare condition but its possible if a program keeps on
opening/closing the port. It has been observed in particular with systemd
boot messages that were causing a kernel panic because of this behavior.
Moving the timer deletion to the beginning of the function stops a tasklet from
being scheduled unexpectedly.
Signed-off-by: Marek Roszko <mark.roszko@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx> # v3.12
[nicolas.ferre@xxxxxxxxx: modify commit message, call setup_timer() in any case]
Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
---
drivers/tty/serial/atmel_serial.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 2b6ac1be00d3..a49f10d269b2 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -825,9 +825,6 @@ static void atmel_release_rx_dma(struct uart_port *port)
atmel_port->desc_rx = NULL;
atmel_port->chan_rx = NULL;
atmel_port->cookie_rx = -EINVAL;
-
- if (!atmel_port->is_usart)
- del_timer_sync(&atmel_port->uart_timer);
}
static void atmel_rx_from_dma(struct uart_port *port)
@@ -1229,9 +1226,6 @@ static void atmel_release_rx_pdc(struct uart_port *port)
DMA_FROM_DEVICE);
kfree(pdc->buf);
}
-
- if (!atmel_port->is_usart)
- del_timer_sync(&atmel_port->uart_timer);
}
static void atmel_rx_from_pdc(struct uart_port *port)
@@ -1604,12 +1598,13 @@ static int atmel_startup(struct uart_port *port)
/* enable xmit & rcvr */
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
+ setup_timer(&atmel_port->uart_timer,
+ atmel_uart_timer_callback,
+ (unsigned long)port);
+
if (atmel_use_pdc_rx(port)) {
/* set UART timeout */
if (!atmel_port->is_usart) {
- setup_timer(&atmel_port->uart_timer,
- atmel_uart_timer_callback,
- (unsigned long)port);
mod_timer(&atmel_port->uart_timer,
jiffies + uart_poll_timeout(port));
/* set USART timeout */
@@ -1624,9 +1619,6 @@ static int atmel_startup(struct uart_port *port)
} else if (atmel_use_dma_rx(port)) {
/* set UART timeout */
if (!atmel_port->is_usart) {
- setup_timer(&atmel_port->uart_timer,
- atmel_uart_timer_callback,
- (unsigned long)port);
mod_timer(&atmel_port->uart_timer,
jiffies + uart_poll_timeout(port));
/* set USART timeout */
@@ -1652,6 +1644,12 @@ static void atmel_shutdown(struct uart_port *port)
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
/*
+ * Prevent any tasklets being scheduled during
+ * cleanup
+ */
+ del_timer_sync(&atmel_port->uart_timer);
+
+ /*
* Clear out any scheduled tasklets before
* we destroy the buffers
*/
--
1.8.2.2
--
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