From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] wimax/i2400m: fix erroneous NETDEV_TX_BUSY use Date: Wed, 14 Mar 2012 12:21:44 -0700 Message-ID: <1331752904.6022.53.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Inaky Perez-Gonzalez To: David Miller Return-path: Received: from mail-pz0-f52.google.com ([209.85.210.52]:33398 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761382Ab2CNTVq (ORCPT ); Wed, 14 Mar 2012 15:21:46 -0400 Received: by dadp12 with SMTP id p12so3392397dad.11 for ; Wed, 14 Mar 2012 12:21:46 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: A driver start_xmit() method cannot free skb and return NETDEV_TX_BUSY, since caller is going to reuse freed skb. In fact netif_tx_stop_queue() / netif_stop_queue() is needed before returning NETDEV_TX_BUSY or you can trigger a ksoftirqd fatal loop. In case of memory allocation error, only safe way is to drop the packet and return NETDEV_TX_OK Also increments tx_dropped counter Signed-off-by: Eric Dumazet Cc: Inaky Perez-Gonzalez --- drivers/net/wimax/i2400m/netdev.c | 30 +++++++++------------------- 1 file changed, 10 insertions(+), 20 deletions(-) diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c index 64a1106..63e4b70 100644 --- a/drivers/net/wimax/i2400m/netdev.c +++ b/drivers/net/wimax/i2400m/netdev.c @@ -367,38 +367,28 @@ netdev_tx_t i2400m_hard_start_xmit(struct sk_buff *skb, { struct i2400m *i2400m = net_dev_to_i2400m(net_dev); struct device *dev = i2400m_dev(i2400m); - int result; + int result = -1; d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev); - if (skb_header_cloned(skb)) { - /* - * Make tcpdump/wireshark happy -- if they are - * running, the skb is cloned and we will overwrite - * the mac fields in i2400m_tx_prep_header. Expand - * seems to fix this... - */ - result = pskb_expand_head(skb, 0, 0, GFP_ATOMIC); - if (result) { - result = NETDEV_TX_BUSY; - goto error_expand; - } - } + + if (skb_header_cloned(skb) && + pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) + goto drop; if (i2400m->state == I2400M_SS_IDLE) result = i2400m_net_wake_tx(i2400m, net_dev, skb); else result = i2400m_net_tx(i2400m, net_dev, skb); - if (result < 0) + if (result < 0) { +drop: net_dev->stats.tx_dropped++; - else { + } else { net_dev->stats.tx_packets++; net_dev->stats.tx_bytes += skb->len; } - result = NETDEV_TX_OK; -error_expand: - kfree_skb(skb); + dev_kfree_skb(skb); d_fnend(3, dev, "(skb %p net_dev %p) = %d\n", skb, net_dev, result); - return result; + return NETDEV_TX_OK; }