From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Potential race in ip4_datagram_release_cb Date: Fri, 06 Jun 2014 05:56:15 -0700 Message-ID: <1402059375.3645.284.camel@edumazet-glaptop2.roam.corp.google.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, Kostya Serebryany , Dmitry Vyukov , Lars Bull , Eric Dumazet , Bruce Curtis , Maciej =?UTF-8?Q?=C5=BBenczykowski?= To: Alexey Preobrazhensky Return-path: Received: from mail-pb0-f52.google.com ([209.85.160.52]:34403 "EHLO mail-pb0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750921AbaFFM4R (ORCPT ); Fri, 6 Jun 2014 08:56:17 -0400 Received: by mail-pb0-f52.google.com with SMTP id rr13so2443673pbb.25 for ; Fri, 06 Jun 2014 05:56:17 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2014-06-06 at 15:29 +0400, Alexey Preobrazhensky wrote: > Hello, >=20 > I=E2=80=99m working on AddressSanitizer[1] -- a tool that detects > use-after-free and out-of-bounds bugs in kernel. >=20 > We=E2=80=99ve encountered a heap-use-after-free in ip4_datagram_relea= se_cb() > in linux kernel 3.15-rc5 (revision > 60b5f90d0fac7585f1a43ccdad06787b97eda0ab). >=20 > It seems to be a race between dst_release() and > ip4_datagram_release_cb() on an object from ip_dst_cache slab, all > during the ip4_datagram_connect() call. >=20 > This heap-use-after-free was triggered under trinity syscall fuzzer, > so there is no reproducer. >=20 > It would be great if someone familiar with the code took time to look > into this report. >=20 > Thanks, > Alexey >=20 > [1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizer= =46orKernel >=20 >=20 > AddressSanitizer: heap-use-after-free in ipv4_dst_check > Read of size 2 by thread T15453: > [] ipv4_dst_check+0x1a/0x90 ./net/ipv4/route.c:111= 6 > [] __sk_dst_check+0x89/0xe0 ./net/core/sock.c:531 > [] ip4_datagram_release_cb+0x46/0x390 ??:0 > [] release_sock+0x17a/0x230 ./net/core/sock.c:2413 > [] ip4_datagram_connect+0x462/0x5d0 ??:0 > [] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet= =2Ec:534 > [] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701 > [] SyS_connect+0xe/0x10 ./net/socket.c:1682 > [] system_call_fastpath+0x16/0x1b > ./arch/x86/kernel/entry_64.S:629 >=20 > Freed by thread T15455: > [] dst_destroy+0xa8/0x160 ./net/core/dst.c:251 > [] dst_release+0x45/0x80 ./net/core/dst.c:280 > [] ip4_datagram_connect+0xa1/0x5d0 ??:0 > [] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet= =2Ec:534 > [] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701 > [] SyS_connect+0xe/0x10 ./net/socket.c:1682 > [] system_call_fastpath+0x16/0x1b > ./arch/x86/kernel/entry_64.S:629 >=20 > Allocated by thread T15453: > [] dst_alloc+0x81/0x2b0 ./net/core/dst.c:171 > [] rt_dst_alloc+0x47/0x50 ./net/ipv4/route.c:1406 > [< inlined >] __ip_route_output_key+0x3e8/0xf70 > __mkroute_output ./net/ipv4/route.c:1939 > [] __ip_route_output_key+0x3e8/0xf70 ./net/ipv4/ro= ute.c:2161 > [] ip_route_output_flow+0x14/0x30 ./net/ipv4/route= =2Ec:2249 > [] ip4_datagram_connect+0x317/0x5d0 ??:0 > [] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet= =2Ec:534 > [] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701 > [] SyS_connect+0xe/0x10 ./net/socket.c:1682 > [] system_call_fastpath+0x16/0x1b > ./arch/x86/kernel/entry_64.S:629 >=20 > The buggy address ffff880024ff2266 is located 102 bytes inside > of 192-byte region [ffff880024ff2200, ffff880024ff22c0) >=20 > Memory state around the buggy address: > ffff880024ff1d00: ffffffff fffrrrrr rrrrrrrr rrrrrrrr > ffff880024ff1e00: ffffffff ffffffff ffffffff fffrrrrr > ffff880024ff1f00: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr > ffff880024ff2000: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr > ffff880024ff2100: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr > >ffff880024ff2200: ffffffff ffffffff ffffffff rrrrrrrr > ^ > ffff880024ff2300: rrrrrrrr rrrrrrrr ........ ........ > ffff880024ff2400: ........ rrrrrrrr rrrrrrrr rrrrrrrr > ffff880024ff2500: ffffffff ffffffff ffffffff rrrrrrrr > ffff880024ff2600: rrrrrrrr rrrrrrrr ffffffff ffffffff > ffff880024ff2700: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr > Legend: > f - 8 freed bytes > r - 8 redzone bytes > . - 8 allocated bytes > x=3D1..7 - x allocated bytes + (8-x) redzone bytes > -- Yeah, we had many reports in the past that something was wrong ... Your nice report made me take a look, finally :( Problem comes from net/ipv4/udp.c:1008: sk_dst_set(sk, dst_clone(&rt->d= st)); Could you try following patch ? Thanks ! diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 4468e1adc094..d5e68ee63b8f 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1004,8 +1004,11 @@ int udp_sendmsg(struct kiocb *iocb, struct sock = *sk, struct msghdr *msg, if ((rt->rt_flags & RTCF_BROADCAST) && !sock_flag(sk, SOCK_BROADCAST)) goto out; - if (connected) - sk_dst_set(sk, dst_clone(&rt->dst)); + if (connected) { + spin_lock_bh(&sk->sk_lock.slock); + __sk_dst_set(sk, dst_clone(&rt->dst)); + spin_unlock_bh(&sk->sk_lock.slock); + } } =20 if (msg->msg_flags&MSG_CONFIRM)