2019-03-14 07:19:16

by Kangjie Lu

Subject: [PATCH] tty: atmel_serial: fix a NULL pointer dereference

In case dmaengine_prep_dma_cyclic fails, the fix return a proper
error code to avoid NULL pointer dereference.

Signed-off-by: Kangjie Lu <[email protected]>
---
drivers/tty/serial/atmel_serial.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 05147fe24343..cf560d05008c 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1237,8 +1237,10 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
dma_cap_set(DMA_CYCLIC, mask);

atmel_port->chan_rx = dma_request_slave_channel(mfd_dev, "rx");
- if (atmel_port->chan_rx == NULL)
+ if (atmel_port->chan_rx == NULL) {
+ ret = -EINVAL;
goto chan_err;
+ }
dev_info(port->dev, "using %s for rx DMA transfers\n",
dma_chan_name(atmel_port->chan_rx));

@@ -1257,6 +1259,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)

if (!nent) {
dev_dbg(port->dev, "need to release resource of dma\n");
+ ret = -EINVAL;
goto chan_err;
} else {
dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", __func__,
@@ -1288,6 +1291,11 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
sg_dma_len(&atmel_port->sg_rx)/2,
DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT);
+ if (!desc) {
+ dev_err(port->dev, "Preparing DMA cyclic failed\n");
+ ret = -ENOMEM;
+ goto chan_err;
+ }
desc->callback = atmel_complete_rx_dma;
desc->callback_param = port;
atmel_port->desc_rx = desc;
@@ -1300,7 +1308,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
atmel_port->use_dma_rx = 0;
if (atmel_port->chan_rx)
atmel_release_rx_dma(port);
- return -EINVAL;
+ return ret;
}

static void atmel_uart_timer_callback(struct timer_list *t)
--
2.17.1

2019-03-14 08:34:27

by Richard Genoud

Subject: Re: [PATCH] tty: atmel_serial: fix a NULL pointer dereference

Hi,

Good catch !
Le 14/03/2019 à 08:17, Kangjie Lu a écrit :
> In case dmaengine_prep_dma_cyclic fails, the fix return a proper
> error code to avoid NULL pointer dereference.
>
you could add:
Fixes: 34df42f59a60 ("serial: at91: add rx dma support")
So that -stable branches get this.

> Signed-off-by: Kangjie Lu <[email protected]>
> ---
> drivers/tty/serial/atmel_serial.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 05147fe24343..cf560d05008c 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1237,8 +1237,10 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
> dma_cap_set(DMA_CYCLIC, mask);
>
> atmel_port->chan_rx = dma_request_slave_channel(mfd_dev, "rx");
> - if (atmel_port->chan_rx == NULL)
> + if (atmel_port->chan_rx == NULL) {
> + ret = -EINVAL;
> goto chan_err;
> + }
> dev_info(port->dev, "using %s for rx DMA transfers\n",
> dma_chan_name(atmel_port->chan_rx));
>
> @@ -1257,6 +1259,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
>
> if (!nent) {
> dev_dbg(port->dev, "need to release resource of dma\n");
> + ret = -EINVAL;
> goto chan_err;
> } else {
> dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", __func__,
> @@ -1288,6 +1291,11 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
> sg_dma_len(&atmel_port->sg_rx)/2,
> DMA_DEV_TO_MEM,
> DMA_PREP_INTERRUPT);
> + if (!desc) {
> + dev_err(port->dev, "Preparing DMA cyclic failed\n");
> + ret = -ENOMEM;
IMHO, we don't really know why dmaengine_prep_dma_cyclic() failed, it
could be because it's already in use, or bad value, or...
(and anyway, we just check if the return value is < 0 in atmel _startup.)
Is there a specific reason you choose -ENOMEM ?
If not, maybe keeping this patch smaller with a simple dev_err()+goto
here would be a better choice.

> + goto chan_err;
> + }
> desc->callback = atmel_complete_rx_dma;
> desc->callback_param = port;
> atmel_port->desc_rx = desc;
> @@ -1300,7 +1308,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
> atmel_port->use_dma_rx = 0;
> if (atmel_port->chan_rx)
> atmel_release_rx_dma(port);
> - return -EINVAL;
> + return ret;
> }
>
> static void atmel_uart_timer_callback(struct timer_list *t)
>

Thanks !

Richard.

2019-03-15 07:22:56

by Kangjie Lu

Subject: [PATCH v2] tty: atmel_serial: fix a NULL pointer dereference

Fixes: 34df42f59a60 ("serial: at91: add rx dma support")

In case dmaengine_prep_dma_cyclic fails, the fix returns a proper
error code to avoid NULL pointer dereference.

Signed-off-by: Kangjie Lu <[email protected]>

---
V2: simplified the patch as suggested by
Richard Genoud <[email protected]>
---
drivers/tty/serial/atmel_serial.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 05147fe24343..41b728d223d1 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1288,6 +1288,10 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
sg_dma_len(&atmel_port->sg_rx)/2,
DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT);
+ if (!desc) {
+ dev_err(port->dev, "Preparing DMA cyclic failed\n");
+ goto chan_err;
+ }
desc->callback = atmel_complete_rx_dma;
desc->callback_param = port;
atmel_port->desc_rx = desc;
--
2.17.1