Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752047AbdCCPUM (ORCPT ); Fri, 3 Mar 2017 10:20:12 -0500 Received: from mail-pg0-f65.google.com ([74.125.83.65]:33086 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751583AbdCCPT7 (ORCPT ); Fri, 3 Mar 2017 10:19:59 -0500 Message-ID: <1488552503.9415.330.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: net/dccp: use-after-free in dccp_feat_activate_values From: Eric Dumazet To: Dmitry Vyukov Cc: Cong Wang , Andrey Konovalov , Gerrit Renker , "David S. Miller" , dccp@vger.kernel.org, netdev , LKML , Eric Dumazet Date: Fri, 03 Mar 2017 06:48:23 -0800 In-Reply-To: <1488551576.9415.328.camel@edumazet-glaptop3.roam.corp.google.com> References:

<1488551576.9415.328.camel@edumazet-glaptop3.roam.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4135 Lines: 98 On Fri, 2017-03-03 at 06:32 -0800, Eric Dumazet wrote: > On Fri, 2017-03-03 at 15:11 +0100, Dmitry Vyukov wrote: > > On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang wrote: > > > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov > > > wrote: > > >> Hi, > > >> > > >> I've got the following error report while fuzzing the kernel with syzkaller. > > >> > > >> On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742. > > >> > > >> A reproducer and .config are attached. > > >> Note, that it takes quite some time to trigger the bug (up to 10 minutes). > > >> > > >> BUG: KASAN: use-after-free in dccp_feat_activate_values+0x967/0xab0 > > >> net/dccp/feat.c:1541 at addr ffff88003713be68 > > >> Read of size 8 by task syz-executor2/8457 > > >> CPU: 2 PID: 8457 Comm: syz-executor2 Not tainted 4.10.0-rc7+ #127 > > >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > > >> Call Trace: > > >> > > >> __dump_stack lib/dump_stack.c:15 [inline] > > >> dump_stack+0x292/0x398 lib/dump_stack.c:51 > > >> kasan_object_err+0x1c/0x70 mm/kasan/report.c:162 > > >> print_address_description mm/kasan/report.c:200 [inline] > > >> kasan_report_error mm/kasan/report.c:289 [inline] > > >> kasan_report.part.1+0x20e/0x4e0 mm/kasan/report.c:311 > > >> kasan_report mm/kasan/report.c:332 [inline] > > >> __asan_report_load8_noabort+0x29/0x30 mm/kasan/report.c:332 > > >> dccp_feat_activate_values+0x967/0xab0 net/dccp/feat.c:1541 > > >> dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121 > > >> dccp_v6_request_recv_sock+0x1f6/0x1960 net/dccp/ipv6.c:457 > > >> dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186 > > >> dccp_v6_rcv+0x69e/0x1d00 net/dccp/ipv6.c:711 > > >> ip6_input_finish+0x46d/0x17a0 net/ipv6/ip6_input.c:279 > > >> NF_HOOK include/linux/netfilter.h:257 [inline] > > >> ip6_input+0xdb/0x590 net/ipv6/ip6_input.c:322 > > >> dst_input include/net/dst.h:507 [inline] > > >> ip6_rcv_finish+0x289/0x890 net/ipv6/ip6_input.c:69 > > >> NF_HOOK include/linux/netfilter.h:257 [inline] > > >> ipv6_rcv+0x12ec/0x23d0 net/ipv6/ip6_input.c:203 > > >> __netif_receive_skb_core+0x1ae5/0x3400 net/core/dev.c:4190 > > >> __netif_receive_skb+0x2a/0x170 net/core/dev.c:4228 > > >> process_backlog+0xe5/0x6c0 net/core/dev.c:4839 > > >> napi_poll net/core/dev.c:5202 [inline] > > >> net_rx_action+0xe70/0x1900 net/core/dev.c:5267 > > >> __do_softirq+0x2fb/0xb7d kernel/softirq.c:284 > > >> do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902 > > > > > > > > > Seems there is a race condition between iterating dccp_feat_entry > > > and freeing it, bh_lock_sock() seems not held in this path. > > > > > > > > Cong, where exactly do we need to add bh_lock_sock()? > > > > I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c > > > I would try : Or something that would compile. I will take a deeper look after my commute. diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c index 409d0cfd34474812c3bf74f26cd423a3d65ee441..56f883b301ccd610fc24efeac4fb47d3c2f95ecf 100644 --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -482,7 +482,11 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req if (dst == NULL) goto out; + /* DCCP is not ready yet for lockless SYN processing */ + bh_lock_sock((struct sock *)sk); skb = dccp_make_response(sk, dst, req); + bh_unlock_sock((struct sock *)sk); + if (skb != NULL) { const struct inet_request_sock *ireq = inet_rsk(req); struct dccp_hdr *dh = dccp_hdr(skb); diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c index 233b57367758c64c09ed40f7359cb8fcb1918d93..673f45f85b7c755c8165c6274ffb6b1fe5660683 100644 --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -214,7 +214,11 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req goto done; } + /* DCCP is not ready yet for lockless SYN processing */ + bh_lock_sock((struct sock *)sk); skb = dccp_make_response(sk, dst, req); + bh_unlock_sock((struct sock *)sk); + if (skb != NULL) { struct dccp_hdr *dh = dccp_hdr(skb); struct ipv6_txoptions *opt;