From patchwork Mon Jan 22 17:06:37 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Guillaume Nault X-Patchwork-Id: 864307 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3zQHsP6b0mz9sDB for ; Tue, 23 Jan 2018 04:06:49 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751139AbeAVRGr (ORCPT ); Mon, 22 Jan 2018 12:06:47 -0500 Received: from zimbra.alphalink.fr ([217.15.80.77]:58114 "EHLO zimbra.alphalink.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751087AbeAVRGq (ORCPT ); Mon, 22 Jan 2018 12:06:46 -0500 Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id D31AB2B5206F; Mon, 22 Jan 2018 18:06:44 +0100 (CET) Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id nq7pIHxyBxwQ; Mon, 22 Jan 2018 18:06:38 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id E48432B520B2; Mon, 22 Jan 2018 18:06:37 +0100 (CET) X-Virus-Scanned: amavisd-new at mail-2-cbv2.admin.alphalink.fr Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id CN0oeA6jLx1e; Mon, 22 Jan 2018 18:06:37 +0100 (CET) Received: from c-dev-0.admin.alphalink.fr (94-84-15-217.reverse.alphalink.fr [217.15.84.94]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id A98252B5206F; Mon, 22 Jan 2018 18:06:37 +0100 (CET) Received: by c-dev-0.admin.alphalink.fr (Postfix, from userid 1000) id 741DE6013B; Mon, 22 Jan 2018 18:06:37 +0100 (CET) Date: Mon, 22 Jan 2018 18:06:37 +0100 From: Guillaume Nault To: netdev@vger.kernel.org Cc: Michal Ostrowski , Johannes Berg , Xin Long Subject: [PATCH net] pppoe: take ->needed_headroom of lower device into account on xmit Message-ID: MIME-Version: 1.0 Content-Disposition: inline X-Mutt-Fcc: =Sent User-Agent: Mutt/1.9.2 (2017-12-15) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In pppoe_sendmsg(), reserving dev->hard_header_len bytes of headroom was probably fine before the introduction of ->needed_headroom in commit f5184d267c1a ("net: Allow netdevices to specify needed head/tailroom"). But now, virtual devices typically advertise the size of their overhead in dev->needed_headroom, so we must also take it into account in skb_reserve(). Allocation size of skb is also updated to take dev->needed_tailroom into account and replace the arbitrary 32 bytes with the real size of a PPPoE header. This issue was discovered by syzbot, who connected a pppoe socket to a gre device which had dev->header_ops->create == ipgre_header and dev->hard_header_len == 0. Therefore, PPPoE didn't reserve any headroom, and dev_hard_header() crashed when ipgre_header() tried to prepend its header to skb->data. skbuff: skb_under_panic: text:000000001d390b3a len:31 put:24 head:00000000d8ed776f data:000000008150e823 tail:0x7 end:0xc0 dev:gre0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:104! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 3670 Comm: syzkaller801466 Not tainted 4.15.0-rc7-next-20180115+ #97 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:skb_panic+0x162/0x1f0 net/core/skbuff.c:100 RSP: 0018:ffff8801d9bd7840 EFLAGS: 00010282 RAX: 0000000000000083 RBX: ffff8801d4f083c0 RCX: 0000000000000000 RDX: 0000000000000083 RSI: 1ffff1003b37ae92 RDI: ffffed003b37aefc RBP: ffff8801d9bd78a8 R08: 1ffff1003b37ae8a R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff86200de0 R13: ffffffff84a981ad R14: 0000000000000018 R15: ffff8801d2d34180 FS: 00000000019c4880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000208bc000 CR3: 00000001d9111001 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: skb_under_panic net/core/skbuff.c:114 [inline] skb_push+0xce/0xf0 net/core/skbuff.c:1714 ipgre_header+0x6d/0x4e0 net/ipv4/ip_gre.c:879 dev_hard_header include/linux/netdevice.h:2723 [inline] pppoe_sendmsg+0x58e/0x8b0 drivers/net/ppp/pppoe.c:890 sock_sendmsg_nosec net/socket.c:630 [inline] sock_sendmsg+0xca/0x110 net/socket.c:640 sock_write_iter+0x31a/0x5d0 net/socket.c:909 call_write_iter include/linux/fs.h:1775 [inline] do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653 do_iter_write+0x154/0x540 fs/read_write.c:932 vfs_writev+0x18a/0x340 fs/read_write.c:977 do_writev+0xfc/0x2a0 fs/read_write.c:1012 SYSC_writev fs/read_write.c:1085 [inline] SyS_writev+0x27/0x30 fs/read_write.c:1082 entry_SYSCALL_64_fastpath+0x29/0xa0 Admittedly PPPoE shouldn't be allowed to run on non Ethernet-like interfaces, but reserving space for ->needed_headroom is a more fundamental issue that needs to be addressed first. Same problem exists for __pppoe_xmit(), which also needs to take dev->needed_headroom into account in skb_cow_head(). Fixes: f5184d267c1a ("net: Allow netdevices to specify needed head/tailroom") Reported-by: syzbot+ed0838d0fa4c4f2b528e20286e6dc63effc7c14d@syzkaller.appspotmail.com Signed-off-by: Guillaume Nault Reviewed-by: Xin Long --- drivers/net/ppp/pppoe.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index 4e1da1645b15..5aa59f41bf8c 100644 --- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -842,6 +842,7 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m, struct pppoe_hdr *ph; struct net_device *dev; char *start; + int hlen; lock_sock(sk); if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED)) { @@ -860,16 +861,16 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m, if (total_len > (dev->mtu + dev->hard_header_len)) goto end; - - skb = sock_wmalloc(sk, total_len + dev->hard_header_len + 32, - 0, GFP_KERNEL); + hlen = LL_RESERVED_SPACE(dev); + skb = sock_wmalloc(sk, hlen + sizeof(*ph) + total_len + + dev->needed_tailroom, 0, GFP_KERNEL); if (!skb) { error = -ENOMEM; goto end; } /* Reserve space for headers. */ - skb_reserve(skb, dev->hard_header_len); + skb_reserve(skb, hlen); skb_reset_network_header(skb); skb->dev = dev; @@ -930,7 +931,7 @@ static int __pppoe_xmit(struct sock *sk, struct sk_buff *skb) /* Copy the data if there is no space for the header or if it's * read-only. */ - if (skb_cow_head(skb, sizeof(*ph) + dev->hard_header_len)) + if (skb_cow_head(skb, LL_RESERVED_SPACE(dev) + sizeof(*ph))) goto abort; __skb_push(skb, sizeof(*ph));