Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752872AbaLXMbp (ORCPT ); Wed, 24 Dec 2014 07:31:45 -0500 Received: from mail-lb0-f172.google.com ([209.85.217.172]:63214 "EHLO mail-lb0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752161AbaLXMbm (ORCPT ); Wed, 24 Dec 2014 07:31:42 -0500 MIME-Version: 1.0 In-Reply-To: <20141223154654.GB6460@vivalin-002> References: <20141223154654.GB6460@vivalin-002> From: Olivier Sobrie Date: Wed, 24 Dec 2014 13:31:20 +0100 X-Google-Sender-Auth: JotjjYrFXusE1qWjhQnJPk9_6EY Message-ID: Subject: Re: [PATCH] can: kvaser_usb: Don't free packets when tight on URBs To: "Ahmed S. Darwish" Cc: Oliver Hartkopp , Wolfgang Grandegger , Marc Kleine-Budde , "David S. Miller" , Paul Gortmaker , Linux-CAN , netdev , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Ahmed, On Tue, Dec 23, 2014 at 05:46:54PM +0200, Ahmed S. Darwish wrote: > From: Ahmed S. Darwish > > 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 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; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/