Messages in this thread | | | From | Olivier Sobrie <> | Date | Wed, 24 Dec 2014 13:31:20 +0100 | Subject | Re: [PATCH] can: kvaser_usb: Don't free packets when tight on URBs |
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Hello Ahmed,
On Tue, Dec 23, 2014 at 05:46:54PM +0200, Ahmed S. Darwish wrote: > From: Ahmed S. Darwish <ahmed.darwish@valeo.com> > > 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. > > Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
Thank you for the fix.
> --- > drivers/net/can/usb/kvaser_usb.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > (Generated over 3.19.0-rc1) > > diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c > index 541fb7a..34c35d8 100644 > --- a/drivers/net/can/usb/kvaser_usb.c > +++ b/drivers/net/can/usb/kvaser_usb.c > @@ -1286,6 +1286,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb, > struct kvaser_msg *msg; > int i, err; > int ret = NETDEV_TX_OK; > + bool kfree_skb_on_error = true; > > if (can_dropped_invalid_skb(netdev, skb)) > return NETDEV_TX_OK; > @@ -1336,6 +1337,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb, > > if (!context) { > netdev_warn(netdev, "cannot find free context\n"); > + kfree_skb_on_error = false;
Instead of using an extra variable, you can also set skb to NULL here. Or maybe better, you can move the dev_kfree_skb() in the two previous tests (in the check of variables urb and buf).
Thank you,
Olivier
> ret = NETDEV_TX_BUSY; > goto releasebuf; > } > @@ -1364,8 +1366,7 @@ 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) */ > + kfree_skb_on_error = false; > > atomic_dec(&priv->active_tx_urbs); > usb_unanchor_urb(urb); > @@ -1389,7 +1390,8 @@ releasebuf: > nobufmem: > usb_free_urb(urb); > nourbmem: > - dev_kfree_skb(skb); > + if (kfree_skb_on_error) > + dev_kfree_skb(skb); > return ret; > } >
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