From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754138AbbAERtR (ORCPT ); Mon, 5 Jan 2015 12:49:17 -0500 Received: from mail-wi0-f182.google.com ([209.85.212.182]:56718 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752817AbbAERtP (ORCPT ); Mon, 5 Jan 2015 12:49:15 -0500 Date: Mon, 5 Jan 2015 12:49:10 -0500 From: "Ahmed S. Darwish" To: Olivier Sobrie , Oliver Hartkopp , Wolfgang Grandegger , Marc Kleine-Budde Cc: "David S. Miller" , Paul Gortmaker , Linux-CAN , netdev , LKML Subject: [PATCH v3 1/4] can: kvaser_usb: Don't free packets when tight on URBs Message-ID: <20150105174910.GA6304@linux> References: <20141223154654.GB6460@vivalin-002> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141223154654.GB6460@vivalin-002> 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 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. 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. Signed-off-by: Ahmed S. Darwish Acked-by: Olivier Sobrie --- drivers/net/can/usb/kvaser_usb.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) ** V3 Changelog: - checkpatch.pl suggestions ('net/' commenting style) diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c index 541fb7a..2e7d513 100644 --- a/drivers/net/can/usb/kvaser_usb.c +++ b/drivers/net/can/usb/kvaser_usb.c @@ -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; }