Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755012AbZFHKp2 (ORCPT ); Mon, 8 Jun 2009 06:45:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753248AbZFHKpQ (ORCPT ); Mon, 8 Jun 2009 06:45:16 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:35926 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752825AbZFHKpP convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 06:45:15 -0400 Message-ID: <4A2CEB9E.7080109@gmail.com> Date: Mon, 08 Jun 2009 12:44:46 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: Vegard Nossum , "David S. Miller" CC: John Dykstra , Linux Netdev List , Ingo Molnar , Pekka Enberg , LKML , Jiri Pirko Subject: [PATCH net-next-2.6] net: loopback device dev->addr_len fix References: <19f34abd0905301323k1498ca3fv31b271de65d60afc@mail.gmail.com> <1244408607.9064.8.camel@Maple> <19f34abd0906080300w796c6b65o6b537064cac917b0@mail.gmail.com> In-Reply-To: <19f34abd0906080300w796c6b65o6b537064cac917b0@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Mon, 08 Jun 2009 12:44:46 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2688 Lines: 74 Vegard Nossum a écrit : > 2009/6/7 John Dykstra : >> On Sat, 2009-05-30 at 22:23 +0200, Vegard Nossum wrote: >>> It seems that loopback's hardware address is never initialized by the >>> kernel. So if userspace attempts to read this address before it has >>> been set, the kernel will return some uninitialized data (only 6 >>> bytes, though). >> Thank you for the report, Vegard. >> >> I've been unable to reproduce the problem you describe, using >> 2.6-30-rc8, this test program and a couple of kernel builds for system >> load: > [...] >> ------------------------------------------------------------------ >> >> Looking at the kernel code, it appears that all bytes of struct >> net_device, including the L2 address, are initialized to zeros at >> interface creation time. >> >> Can you spot a difference between your test procedures and mine that >> would enable me to reproduce the problem? > > Hi, > > I just tried your test program on a linux-next kernel, it works beautifully :-) > > (I made one change: The stack grows downwards on x86, so I think you > should put child_stack + 16386 as the stack to clone()?) > > As I wrote in reply to Stephen Hemminger, this problem seems to be > caused by a particular patch in linux-next: > > commit f001fde5eadd915f4858d22ed70d7040f48767cf > Author: Jiri Pirko > Date: Tue May 5 02:48:28 2009 +0000 > > net: introduce a list of device addresses dev_addr_list (v6) > I believe following patch should fix this problem. Thank you [PATCH net-next-2.6] net: loopback device dev->addr_len fix commit f001fde5eadd915f4858d22ed70d7040f48767cf (net: introduce a list of device addresses dev_addr_list (v6)) added one regression Vegard Nossum found in its testings. loopback device doesnt have a hw address, we should set its dev->addr_len to 0, not ETH_ALEN. Reported-by: Vegard Nossum Signed-off-by: Eric Dumazet --- diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c index da472c6..40ded4e 100644 --- a/drivers/net/loopback.c +++ b/drivers/net/loopback.c @@ -166,7 +166,7 @@ static void loopback_setup(struct net_device *dev) { dev->mtu = (16 * 1024) + 20 + 20 + 12; dev->hard_header_len = ETH_HLEN; /* 14 */ - dev->addr_len = ETH_ALEN; /* 6 */ + dev->addr_len = 0; dev->tx_queue_len = 0; dev->type = ARPHRD_LOOPBACK; /* 0x0001*/ dev->flags = IFF_LOOPBACK; -- 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/