Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756351Ab3HZHjX (ORCPT ); Mon, 26 Aug 2013 03:39:23 -0400 Received: from mail-qe0-f43.google.com ([209.85.128.43]:61259 "EHLO mail-qe0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752449Ab3HZHjV (ORCPT ); Mon, 26 Aug 2013 03:39:21 -0400 Message-ID: <521B0622.9090208@redhat.com> Date: Mon, 26 Aug 2013 09:39:14 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 MIME-Version: 1.0 To: Alexander Graf CC: Yann Droneaud , Gleb Natapov , Benjamin Herrenschmidt , Paul Mackerras , Alex Williamson , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] ppc: kvm: use anon_inode_getfd() with O_CLOEXEC flag References: <3557EF65-4327-4DAE-999A-B0EE13C433F5@suse.de> In-Reply-To: <3557EF65-4327-4DAE-999A-B0EE13C433F5@suse.de> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1575 Lines: 36 Il 25/08/2013 17:04, Alexander Graf ha scritto: > > On 24.08.2013, at 21:14, Yann Droneaud wrote: > >> KVM uses anon_inode_get() to allocate file descriptors as part >> of some of its ioctls. But those ioctls are lacking a flag argument >> allowing userspace to choose options for the newly opened file descriptor. >> >> In such case it's advised to use O_CLOEXEC by default so that >> userspace is allowed to choose, without race, if the file descriptor >> is going to be inherited across exec(). >> >> This patch set O_CLOEXEC flag on all file descriptors created >> with anon_inode_getfd() to not leak file descriptors across exec(). >> >> Signed-off-by: Yann Droneaud >> Link: http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@opteya.com > > Reviewed-by: Alexander Graf > > Would it make sense to simply inherit the O_CLOEXEC flag from the > parent kvm fd instead? That would give user space the power to keep > fds across exec() if it wants to. Does it make sense to use non-O_CLOEXEC file descriptors with KVM at all? Besides fork() not being supported by KVM, as described in Documentation/virtual/kvm/api.txt, the VMAs of the parent process go away as soon as you exec(). I'm not sure how you can use the inherited file descriptor in a sensible way after exec(). Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/