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can: kvaser_usb: Don't free packets when tight on URBs

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Flooding the Kvaser CAN to USB dongle with multiple reads and
writes in high frequency caused seemingly-random panics in the
kernel.

On further inspection, it seems the driver erroneously freed the
to-be-transmitted packet upon getting tight on URBs and returning
NETDEV_TX_BUSY, leading to invalid memory writes and double frees
at a later point in time.

Note:

Finding no more URBs/transmit-contexts and returning NETDEV_TX_BUSY
is a driver bug in and out of itself: it means that our start/stop
queue flow control is broken.

This patch only fixes the (buggy) error handling code; the root
cause shall be fixed in a later commit.

Acked-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Ahmed S. Darwish 2015-01-05 12:49:10 -05:00 committed by Marc Kleine-Budde
parent 47e3485af0
commit b442723fce
1 changed files with 4 additions and 6 deletions
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10
drivers/net/can/usb/kvaser_usb.c
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@ -1294,12 +1294,14 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
if (!urb) {
netdev_err(netdev, "No memory left for URBs\n");
stats->tx_dropped++;
goto nourbmem;
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}
buf = kmalloc(sizeof(struct kvaser_msg), GFP_ATOMIC);
if (!buf) {
stats->tx_dropped++;
dev_kfree_skb(skb);
goto nobufmem;
}
@ -1334,6 +1336,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
}
}
/* This should never happen; it implies a flow control bug */
if (!context) {
netdev_warn(netdev, "cannot find free context\n");
ret = NETDEV_TX_BUSY;
@ -1364,9 +1367,6 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
if (unlikely(err)) {
can_free_echo_skb(netdev, context->echo_index);
skb = NULL; /* set to NULL to avoid double free in
* dev_kfree_skb(skb) */
atomic_dec(&priv->active_tx_urbs);
usb_unanchor_urb(urb);
@ -1388,8 +1388,6 @@ releasebuf:
kfree(buf);
nobufmem:
usb_free_urb(urb);
nourbmem:
dev_kfree_skb(skb);
return ret;
}