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Message-ID: <2375c9f90910190206k67dece39i34f484e0645254b9@mail.gmail.com> Date: Mon, 19 Oct 2009 17:06:08 +0800 From: Américo Wang <xiyou.wangcong@...il.com> To: Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com> Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, alan@...rguk.ukuu.org.uk, davem@...emloft.net, satoshi.oshima.fk@...achi.com, hidehiro.kawai.ez@...achi.com, hideo.aoki.tk@...achi.com, masanori.yoshida.tv@...achi.com Subject: Re: [PATCH] AF_UNIX: Fix deadlock on connecting to shutdown socket On Mon, Oct 19, 2009 at 4:58 PM, Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com> wrote: > Hi, thanks for testing! > > Américo Wang wrote: >> On Mon, Oct 19, 2009 at 2:02 PM, Tomoki Sekiyama >> <tomoki.sekiyama.qu@...achi.com> wrote: >>> Hi, >>> I found a deadlock bug in UNIX domain socket, which makes able to DoS >>> 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 sockets >>> 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... >> >> I tried this with the following command: >> >> % for i in `seq 1 $(grep processor -c /proc/cpuinfo)`; >> do ./unix-socket-dos-exploit; echo "=====$i====";done > <snip> >> My system doesn't hang at all. >> >> 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). Hmm, you are right. My system hangs for 10 or more seconds after I did what you said. Confirmed. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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