Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752118AbdCCPjK (ORCPT ); Fri, 3 Mar 2017 10:39:10 -0500 Received: from mail-ua0-f171.google.com ([209.85.217.171]:36531 "EHLO mail-ua0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751583AbdCCPgt (ORCPT ); Fri, 3 Mar 2017 10:36:49 -0500 MIME-Version: 1.0 In-Reply-To: <1488551576.9415.328.camel@edumazet-glaptop3.roam.corp.google.com> References:

<1488551576.9415.328.camel@edumazet-glaptop3.roam.corp.google.com> From: Dmitry Vyukov Date: Fri, 3 Mar 2017 15:42:16 +0100 Message-ID: Subject: Re: net/dccp: use-after-free in dccp_feat_activate_values To: Eric Dumazet Cc: Cong Wang , Andrey Konovalov , Gerrit Renker , "David S. Miller" , dccp@vger.kernel.org, netdev , LKML , Eric Dumazet Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3913 Lines: 91 On Fri, Mar 3, 2017 at 3:32 PM, Eric Dumazet 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 : > > diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c > index 409d0cfd34474812c3bf74f26cd423a3d65ee441..5a8b5ac5edaaf35428ab04cc810d98310bd169ed 100644 > --- a/net/dccp/ipv4.c > +++ b/net/dccp/ipv4.c > @@ -482,7 +482,9 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req > if (dst == NULL) > goto out; > > + bh_lock_sock(sk); > skb = dccp_make_response(sk, dst, req); > + bh_unlock_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..e89cc88d14c22d411a91afab093e209fcbb816d8 100644 > --- a/net/dccp/ipv6.c > +++ b/net/dccp/ipv6.c > @@ -214,7 +214,9 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req > goto done; > } > > + bh_lock_sock(sk); > skb = dccp_make_response(sk, dst, req); > + bh_unlock_sock(sk); > if (skb != NULL) { > struct dccp_hdr *dh = dccp_hdr(skb); > struct ipv6_txoptions *opt; Applied on bots. Thanks!