From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71462C432C3 for ; Wed, 20 Nov 2019 15:44:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C6192070B for ; Wed, 20 Nov 2019 15:44:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732296AbfKTPn5 (ORCPT ); Wed, 20 Nov 2019 10:43:57 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:52884 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731000AbfKTPkT (ORCPT ); Wed, 20 Nov 2019 10:40:19 -0500 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iXS5V-0004bT-1H; Wed, 20 Nov 2019 15:40:13 +0000 Received: from ben by deadeye with local (Exim 4.93-RC1) (envelope-from ) id 1iXS5U-0004Ie-07; Wed, 20 Nov 2019 15:40:12 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Eric Dumazet" , "syzbot" , "David S. Miller" Date: Wed, 20 Nov 2019 15:37:50 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 40/83] net/packet: fix race in tpacket_snd() In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.78-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 32d3182cd2cd29b2e7e04df7b0db350fbe11289f upstream. packet_sendmsg() checks tx_ring.pg_vec to decide if it must call tpacket_snd(). Problem is that the check is lockless, meaning another thread can issue a concurrent setsockopt(PACKET_TX_RING ) to flip tx_ring.pg_vec back to NULL. Given that tpacket_snd() grabs pg_vec_lock mutex, we can perform the check again to solve the race. syzbot reported : kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 11429 Comm: syz-executor394 Not tainted 5.3.0-rc4+ #101 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:packet_lookup_frame+0x8d/0x270 net/packet/af_packet.c:474 Code: c1 ee 03 f7 73 0c 80 3c 0e 00 0f 85 cb 01 00 00 48 8b 0b 89 c0 4c 8d 24 c1 48 b8 00 00 00 00 00 fc ff df 4c 89 e1 48 c1 e9 03 <80> 3c 01 00 0f 85 94 01 00 00 48 8d 7b 10 4d 8b 3c 24 48 b8 00 00 RSP: 0018:ffff88809f82f7b8 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8880a45c7030 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 1ffff110148b8e06 RDI: ffff8880a45c703c RBP: ffff88809f82f7e8 R08: ffff888087aea200 R09: fffffbfff134ae50 R10: fffffbfff134ae4f R11: ffffffff89a5727f R12: 0000000000000000 R13: 0000000000000001 R14: ffff8880a45c6ac0 R15: 0000000000000000 FS: 00007fa04716f700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa04716edb8 CR3: 0000000091eb4000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: packet_current_frame net/packet/af_packet.c:487 [inline] tpacket_snd net/packet/af_packet.c:2667 [inline] packet_sendmsg+0x590/0x6250 net/packet/af_packet.c:2975 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0xd7/0x130 net/socket.c:657 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2311 __sys_sendmmsg+0x1bf/0x4d0 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2439 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/packet/af_packet.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2286,6 +2286,13 @@ static int tpacket_snd(struct packet_soc mutex_lock(&po->pg_vec_lock); + /* packet_sendmsg() check on tx_ring.pg_vec was lockless, + * we need to confirm it under protection of pg_vec_lock. + */ + if (unlikely(!po->tx_ring.pg_vec)) { + err = -EBUSY; + goto out; + } if (likely(saddr == NULL)) { dev = packet_cached_dev_get(po); proto = po->num;