Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751386AbaLXPw6 (ORCPT ); Wed, 24 Dec 2014 10:52:58 -0500 Received: from mail-wi0-f179.google.com ([209.85.212.179]:48367 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751074AbaLXPw5 (ORCPT ); Wed, 24 Dec 2014 10:52:57 -0500 Date: Wed, 24 Dec 2014 17:52:46 +0200 From: "Ahmed S. Darwish" To: Olivier Sobrie Cc: Oliver Hartkopp , Wolfgang Grandegger , Marc Kleine-Budde , "David S. Miller" , Paul Gortmaker , Linux-CAN , netdev , LKML Subject: Re: [PATCH] can: kvaser_usb: Don't free packets when tight on URBs Message-ID: <20141224155246.GB27062@vivalin-002> References: <20141223154654.GB6460@vivalin-002> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Olivier, On Wed, Dec 24, 2014 at 01:31:20PM +0100, Olivier Sobrie wrote: > 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). > Nice, I'll move dev_kfree_skb() to the two earlier tests then. Thanks, P.S. mailer and patch identation; had to manually fix them before replying (but thanks for the quick review, ofc ;-)) > 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/