Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758650AbbBFMiR (ORCPT ); Fri, 6 Feb 2015 07:38:17 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:40864 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754857AbbBFMBj (ORCPT ); Fri, 6 Feb 2015 07:01:39 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Ahmed S. Darwish" , Marc Kleine-Budde , Luis Henriques Subject: [PATCH 3.16.y-ckt 020/135] can: kvaser_usb: Don't free packets when tight on URBs Date: Fri, 6 Feb 2015 11:59:58 +0000 Message-Id: <1423224113-10958-21-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1423224113-10958-1-git-send-email-luis.henriques@canonical.com> References: <1423224113-10958-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2722 Lines: 89 3.16.7-ckt6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: "Ahmed S. Darwish" commit b442723fcec445fb0ae1104888dd22cd285e0a91 upstream. 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 Signed-off-by: Ahmed S. Darwish Signed-off-by: Marc Kleine-Budde Signed-off-by: Luis Henriques --- drivers/net/can/usb/kvaser_usb.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c index 541fb7a05625..2e7d513a7c11 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; } -- 2.1.4 -- 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/