[PATCH 3.19 138/175] serial: fsl_lpuart: delete timer on shutdown

Greg Kroah-Hartman
2015-03-04T06:30:10Z

From: Stefan Agner <stefan@agner.ch>

commit 4a8588a1cf867333187d9ff071e6fbdab587d194 upstream.

If the serial port gets closed while a RX transfer is in progress,
the timer might fire after the serial port shutdown finished. This
leads in a NULL pointer dereference:

[ 7.508324] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 7.516590] pgd = 86348000
[ 7.519445] [00000000] *pgd=86179831, *pte=00000000, *ppte=00000000
[ 7.526145] Internal error: Oops: 17 [#1] ARM
[ 7.530611] Modules linked in:
[ 7.533876] CPU: 0 PID: 123 Comm: systemd Not tainted 3.19.0-rc3-00004-g5b11ea7 #1778
[ 7.541827] Hardware name: Freescale Vybrid VF610 (Device Tree)
[ 7.547862] task: 861c3400 ti: 86ac8000 task.ti: 86ac8000
[ 7.553392] PC is at lpuart_timer_func+0x24/0xf8
[ 7.558127] LR is at lpuart_timer_func+0x20/0xf8
[ 7.562857] pc : [<802df99c>] lr : [<802df998>] psr: 600b0113
[ 7.562857] sp : 86ac9b90 ip : 86ac9b90 fp : 86ac9bbc
[ 7.574467] r10: 80817180 r9 : 80817b98 r8 : 80817998
[ 7.579803] r7 : 807acee0 r6 : 86989000 r5 : 00000100 r4 : 86997210
[ 7.586444] r3 : 86ac8000 r2 : 86ac9bc0 r1 : 86997210 r0 : 00000000
[ 7.593085] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 7.600341] Control: 10c5387d Table: 86348059 DAC: 00000015
[ 7.606203] Process systemd (pid: 123, stack limit = 0x86ac8230)

Setup the timer on UART startup which allows to delete the timer
unconditionally on shutdown. This also saves the initialization
on each transfer.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/fsl_lpuart.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -506,9 +506,6 @@ static inline void lpuart_prepare_rx(str

spin_lock_irqsave(&sport->port.lock, flags);

- init_timer(&sport->lpuart_timer);
- sport->lpuart_timer.function = lpuart_timer_func;
- sport->lpuart_timer.data = (unsigned long)sport;
sport->lpuart_timer.expires = jiffies + sport->dma_rx_timeout;
add_timer(&sport->lpuart_timer);

@@ -1106,6 +1103,8 @@ static int lpuart_startup(struct uart_po
sport->lpuart_dma_use = false;
} else {
sport->lpuart_dma_use = true;
+ setup_timer(&sport->lpuart_timer, lpuart_timer_func,
+ (unsigned long)sport);
temp = readb(port->membase + UARTCR5);
writeb(temp | UARTCR5_TDMAS, port->membase + UARTCR5);
}
@@ -1180,6 +1179,8 @@ static void lpuart_shutdown(struct uart_
devm_free_irq(port->dev, port->irq, sport);

if (sport->lpuart_dma_use) {
+ del_timer_sync(&sport->lpuart_timer);
+
lpuart_dma_tx_free(port);
lpuart_dma_rx_free(port);
}