From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomoki Sekiyama Subject: Re: [PATCH] AF_UNIX: Fix deadlock on connecting to shutdown socket Date: Mon, 19 Oct 2009 17:58:05 +0900 Message-ID: <4ADC2A1D.2090303@hitachi.com> References: <4ADC010C.5070809@hitachi.com> <2375c9f90910190002m372edafq9a4c95d754640487@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: alan@lxorguk.ukuu.org.uk, davem@davemloft.net, satoshi.oshima.fk@hitachi.com, hidehiro.kawai.ez@hitachi.com, hideo.aoki.tk@hitachi.com, masanori.yoshida.tv@hitachi.com To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: In-Reply-To: <2375c9f90910190002m372edafq9a4c95d754640487@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi, thanks for testing! Am=C3=A9rico Wang wrote: > On Mon, Oct 19, 2009 at 2:02 PM, Tomoki Sekiyama > wrote: >> Hi, >> I found a deadlock bug in UNIX domain socket, which makes able to Do= S >> attack against the local machine by non-root users. >> >> How to reproduce: >> 1. Make a listening AF_UNIX/SOCK_STREAM socket with an abstruct >> namespace(*), and shutdown(2) it. >> 2. Repeat connect(2)ing to the listening socket from the other sock= ets >> until the connection backlog is full-filled. >> 3. connect(2) takes the CPU forever. If every core is taken, the >> system hangs. >> >> PoC code: (Run as many times as cores on SMP machines.) Sorry for my ambiguous explanation ... > Interesting... >=20 > I tried this with the following command: >=20 > % for i in `seq 1 $(grep processor -c /proc/cpuinfo)`; > do ./unix-socket-dos-exploit; echo "=3D=3D=3D=3D=3D$i=3D=3D=3D=3D";do= ne > My system doesn't hang at all. >=20 > Am I missing something? > > Thanks! You should run the ./unix-socket-dos-exploit concurrently, like below: for i in {1..4} ; do ./unix-socket-dos-exploit & done # For safety reason, the PoC code stops in 15 seconds by alarm(15). --=20 Tomoki Sekiyama Linux Technology Center Hitachi, Ltd., Systems Development Laboratory E-mail: tomoki.sekiyama.qu@hitachi.com