[PATCH 4.14 44/88] can: mcba_usb: fix memory leak in mcba_usb

Sasha Levin
2021-06-28T15:09:48Z

From: Pavel Skripkin <paskripkin@gmail.com>

commit 91c02557174be7f72e46ed7311e3bea1939840b0 upstream.

Syzbot reported memory leak in SocketCAN driver for Microchip CAN BUS
Analyzer Tool. The problem was in unfreed usb_coherent.

In mcba_usb_start() 20 coherent buffers are allocated and there is
nothing, that frees them:

1) In callback function the urb is resubmitted and that's all
2) In disconnect function urbs are simply killed, but URB_FREE_BUFFER
is not set (see mcba_usb_start) and this flag cannot be used with
coherent buffers.

Fail log:
| [ 1354.053291][ T8413] mcba_usb 1-1:0.0 can0: device disconnected
| [ 1367.059384][ T8420] kmemleak: 20 new suspected memory leaks (see /sys/kernel/debug/kmem)

So, all allocated buffers should be freed with usb_free_coherent()
explicitly

NOTE:
The same pattern for allocating and freeing coherent buffers
is used in drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c

Fixes: 51f3baad7de9 ("can: mcba_usb: Add support for Microchip CAN BUS Analyzer")
Link: https://lore.kernel.org/r/20210609215833.30393-1-paskripkin@gmail.com
Cc: linux-stable <stable@vger.kernel.org>
Reported-and-tested-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/can/usb/mcba_usb.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
index a09e3f6c2c50..6b0c6009dde0 100644
--- a/drivers/net/can/usb/mcba_usb.c
+++ b/drivers/net/can/usb/mcba_usb.c
@@ -93,6 +93,8 @@ struct mcba_priv {
bool can_ka_first_pass;
bool can_speed_check;
atomic_t free_ctx_cnt;
+ void *rxbuf[MCBA_MAX_RX_URBS];
+ dma_addr_t rxbuf_dma[MCBA_MAX_RX_URBS];
};

/* CAN frame */
@@ -644,6 +646,7 @@ static int mcba_usb_start(struct mcba_priv *priv)
for (i = 0; i < MCBA_MAX_RX_URBS; i++) {
struct urb *urb = NULL;
u8 *buf;
+ dma_addr_t buf_dma;

/* create a URB, and a buffer for it */
urb = usb_alloc_urb(0, GFP_KERNEL);
@@ -653,7 +656,7 @@ static int mcba_usb_start(struct mcba_priv *priv)
}

buf = usb_alloc_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
- GFP_KERNEL, &urb->transfer_dma);
+ GFP_KERNEL, &buf_dma);
if (!buf) {
netdev_err(netdev, "No memory left for USB buffer\n");
usb_free_urb(urb);
@@ -672,11 +675,14 @@ static int mcba_usb_start(struct mcba_priv *priv)
if (err) {
usb_unanchor_urb(urb);
usb_free_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
- buf, urb->transfer_dma);
+ buf, buf_dma);
usb_free_urb(urb);
break;
}

+ priv->rxbuf[i] = buf;
+ priv->rxbuf_dma[i] = buf_dma;
+
/* Drop reference, USB core will take care of freeing it */
usb_free_urb(urb);
}
@@ -719,7 +725,14 @@ static int mcba_usb_open(struct net_device *netdev)

static void mcba_urb_unlink(struct mcba_priv *priv)
{
+ int i;
+
usb_kill_anchored_urbs(&priv->rx_submitted);
+
+ for (i = 0; i < MCBA_MAX_RX_URBS; ++i)
+ usb_free_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
+ priv->rxbuf[i], priv->rxbuf_dma[i]);
+
usb_kill_anchored_urbs(&priv->tx_submitted);
}

--
2.30.2