From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40820) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF5y4-0007WN-Ne for qemu-devel@nongnu.org; Fri, 21 Sep 2012 12:20:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TF5xz-0008BG-VG for qemu-devel@nongnu.org; Fri, 21 Sep 2012 12:20:40 -0400 Received: from indium.canonical.com ([91.189.90.7]:44928) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF5xz-0008BA-PR for qemu-devel@nongnu.org; Fri, 21 Sep 2012 12:20:35 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.71 #1 (Debian)) id 1TF5xy-0000p9-Vb for ; Fri, 21 Sep 2012 16:20:34 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id EDDAB2E806B for ; Fri, 21 Sep 2012 16:20:34 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Fri, 21 Sep 2012 16:13:23 -0000 From: Michal Svoboda Sender: bounces@canonical.com References: <20120921161324.22633.34633.malonedeb@chaenomeles.canonical.com> Message-Id: <20120921161324.22633.34633.malonedeb@chaenomeles.canonical.com> Errors-To: bounces@canonical.com Subject: [Qemu-devel] [Bug 1054180] [NEW] DNS activity in slirp (user networking) mode quickly depletes file descriptors and crashes qemu Reply-To: Bug 1054180 <1054180@bugs.launchpad.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Public bug reported: Hi, we have encountered quite some trouble with filedescriptor depletion of the qemu process. We have figured out that it can be demonstrated easily by doing a lot of DNS queries inside the VM -- in our real world scenario this is caused by running centos network install with a fast mirror. This situation is further problematic because qemu can't handle fd depletio= n very well: 1) if ulimit is 1024 then qemu hangs in infinite loop whenever it tries to = open the 1025th fd 2) setting ulimit >1024 does not help that much because qemu uses select an= d max. fd set size is 1024 per default =3D> qemu crashes because of buffer = overflow in select() 3) setting ulimit > 1024 AND recompiling with large enough fd set size AND = disabling gcc's fortify source seems to work, but that's really just a hot-= fix The problem can be replicated quite easily by running something like while :; do echo >/dev/udp/10.0.2.3/53; done inside a Linux VM -- crash comes very soon. This problem is present in current qemu (1.2.0) and in earlier as well. ** Affects: qemu Importance: Undecided Status: New -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1054180 Title: DNS activity in slirp (user networking) mode quickly depletes file descriptors and crashes qemu Status in QEMU: New Bug description: Hi, we have encountered quite some trouble with filedescriptor depletion of the qemu process. We have figured out that it can be demonstrated easily by doing a lot of DNS queries inside the VM -- in our real world scenario this is caused by running centos network install with a fast mirror. This situation is further problematic because qemu can't handle fd deplet= ion very well: 1) if ulimit is 1024 then qemu hangs in infinite loop whenever it tries t= o open the 1025th fd 2) setting ulimit >1024 does not help that much because qemu uses select = and max. fd set size is 1024 per default =3D> qemu crashes because of buffe= r overflow in select() 3) setting ulimit > 1024 AND recompiling with large enough fd set size AN= D disabling gcc's fortify source seems to work, but that's really just a ho= t-fix The problem can be replicated quite easily by running something like while :; do echo >/dev/udp/10.0.2.3/53; done inside a Linux VM -- crash comes very soon. This problem is present in current qemu (1.2.0) and in earlier as well. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1054180/+subscriptions