From patchwork Wed Nov 5 00:58:33 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Borkmann X-Patchwork-Id: 406848 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 1C8F81400A6 for ; Wed, 5 Nov 2014 11:59:12 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751682AbaKEA6s (ORCPT ); Tue, 4 Nov 2014 19:58:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36934 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256AbaKEA6r (ORCPT ); Tue, 4 Nov 2014 19:58:47 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id sA50wZB7011857 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 4 Nov 2014 19:58:35 -0500 Received: from localhost (vpn1-7-63.ams2.redhat.com [10.36.7.63]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id sA50wXPE011558; Tue, 4 Nov 2014 19:58:34 -0500 From: Daniel Borkmann To: davem@davemloft.net Cc: lw1a2.jing@gmail.com, fw@strlen.de, hannes@stressinduktion.org, netdev@vger.kernel.org, Eric Dumazet , David L Stevens Subject: [PATCH net] ipv6: mld: fix add_grhead skb_over_panic for devs with large MTUs Date: Wed, 5 Nov 2014 01:58:33 +0100 Message-Id: <1415149113-32668-1-git-send-email-dborkman@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It has been reported that generating an MLD listener report on devices with large MTUs (e.g. 9000) and a high number of IPv6 addresses can trigger a skb_over_panic(): skbuff: skb_over_panic: text:ffffffff80612a5d len:3776 put:20 head:ffff88046d751000 data:ffff88046d751010 tail:0xed0 end:0xec0 dev:port1 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:100! invalid opcode: 0000 [#1] SMP Modules linked in: ixgbe(O) CPU: 3 PID: 0 Comm: swapper/3 Tainted: G O 3.14.23+ #4 [...] Call Trace: [] ? skb_put+0x3a/0x3b [] ? add_grhead+0x45/0x8e [] ? add_grec+0x394/0x3d4 [] ? mld_ifc_timer_expire+0x195/0x20d [] ? mld_dad_timer_expire+0x45/0x45 [] ? call_timer_fn.isra.29+0x12/0x68 [] ? run_timer_softirq+0x163/0x182 [] ? __do_softirq+0xe0/0x21d [] ? irq_exit+0x4e/0xd3 [] ? smp_apic_timer_interrupt+0x3b/0x46 [] ? apic_timer_interrupt+0x6a/0x70 mld_newpack() skb allocations are usually requested with dev->mtu in size, since commit 72e09ad107e7 ("ipv6: avoid high order allocations") we have changed the limit in order to be less unreliable to fail. However, in MLD/IGMP code, we have some rather ugly AVAILABLE(skb) macros, which determine if we may end up doing an skb_put() for adding another record. To avoid possible fragmentation, we check the skb's tailroom as skb->dev->mtu - skb->len, which is a wrong assumption as the actual max allocation size will be much smaller. The IGMP case doesn't have this issue as commit 57e1ab6eaddc ("igmp: refine skb allocations") stores the allocation size in the cb[], but therefore takes the MTU check not into account anymore. Add and use skb_nofrag_tailroom() for both cases. Reported-by: lw1a2.jing@gmail.com Fixes: 72e09ad107e7 ("ipv6: avoid high order allocations") Signed-off-by: Daniel Borkmann Cc: Eric Dumazet Cc: David L Stevens --- In skb_nofrag_tailroom(), we could actually omit the !skb->dev check, but I leave that rather as a possible cleanup item for net-next. include/linux/netdevice.h | 15 +++++++++++++++ net/ipv4/igmp.c | 6 +----- net/ipv6/mcast.c | 3 +-- 3 files changed, 17 insertions(+), 7 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 74fd5d3..e4f4cfa 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2262,6 +2262,21 @@ do { \ compute_pseudo(skb, proto)); \ } while (0) +/** + * skb_nofrag_tailroom - bytes at buffer end still fitting into MTU + * @skb: buffer to check + * + * Return the number of bytes of free space at the tail of an sk_buff + * that still fit into the device MTU. + */ +static inline int skb_nofrag_tailroom(const struct sk_buff *skb) +{ + if (!skb->dev) + return skb_tailroom(skb); + + return clamp_t(int, skb->dev->mtu - skb->len, 0, skb_tailroom(skb)); +} + static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev, unsigned short type, const void *daddr, const void *saddr, diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index fb70e3e..a750dfb 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -318,8 +318,6 @@ igmp_scount(struct ip_mc_list *pmc, int type, int gdeleted, int sdeleted) return scount; } -#define igmp_skb_size(skb) (*(unsigned int *)((skb)->cb)) - static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size) { struct sk_buff *skb; @@ -341,7 +339,6 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size) return NULL; } skb->priority = TC_PRIO_CONTROL; - igmp_skb_size(skb) = size; rt = ip_route_output_ports(net, &fl4, NULL, IGMPV3_ALL_MCR, 0, 0, 0, @@ -423,8 +420,7 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ip_mc_list *pmc, return skb; } -#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? igmp_skb_size(skb) - (skb)->len : \ - skb_tailroom(skb)) : 0) +#define AVAILABLE(skb) ((skb) ? skb_nofrag_tailroom(skb) : 0) static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc, int type, int gdeleted, int sdeleted) diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index 9648de2..1bc18f9 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -1690,8 +1690,7 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ifmcaddr6 *pmc, return skb; } -#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? (skb)->dev->mtu - (skb)->len : \ - skb_tailroom(skb)) : 0) +#define AVAILABLE(skb) ((skb) ? skb_nofrag_tailroom(skb) : 0) static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc, int type, int gdeleted, int sdeleted, int crsend)