From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1ZtykJ-00012x-Pd for mharc-qemu-trivial@gnu.org; Wed, 04 Nov 2015 09:09:03 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57883) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtykF-0000y8-PP for qemu-trivial@nongnu.org; Wed, 04 Nov 2015 09:09:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtykB-0007qz-5N for qemu-trivial@nongnu.org; Wed, 04 Nov 2015 09:08:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33245) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ztyk4-0007p4-Hz; Wed, 04 Nov 2015 09:08:48 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 26695811D8; Wed, 4 Nov 2015 14:08:48 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-44.ams2.redhat.com [10.36.116.44]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tA4E8k63022904 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 4 Nov 2015 09:08:47 -0500 Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E201F303F90E; Wed, 4 Nov 2015 15:08:45 +0100 (CET) From: Markus Armbruster To: Paolo Bonzini References: <1446644927-8764-1-git-send-email-pbonzini@redhat.com> Date: Wed, 04 Nov 2015 15:08:45 +0100 In-Reply-To: <1446644927-8764-1-git-send-email-pbonzini@redhat.com> (Paolo Bonzini's message of "Wed, 4 Nov 2015 14:48:47 +0100") Message-ID: <87lhadluvm.fsf@blackfin.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org, crobinso@redhat.com Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Nov 2015 14:09:03 -0000 Paolo Bonzini writes: > Using access() is a time-of-check/time-of-use race condition. It is > okay to use them to provide better error messages, but that is pretty > much it. > > This is not one such case; on the other hand, access() *will* skip > unlink() for a non-existent path, so ignore ENOENT return values from > the unlink() system call. > > Signed-off-by: Paolo Bonzini > --- > util/qemu-sockets.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c > index 9142917..de9145a 100644 > --- a/util/qemu-sockets.c > +++ b/util/qemu-sockets.c > @@ -751,8 +751,7 @@ int unix_listen_opts(QemuOpts *opts, Error **errp) > qemu_opt_set(opts, "path", un.sun_path, &error_abort); > } > > - if ((access(un.sun_path, F_OK) == 0) && > - unlink(un.sun_path) < 0) { > + if (unlink(un.sun_path) < 0 && errno != ENOENT) { > error_setg_errno(errp, errno, > "Failed to unlink socket %s", un.sun_path); > goto err; Reviewed-by: Markus Armbruster From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57770) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtykA-0000ts-Aq for qemu-devel@nongnu.org; Wed, 04 Nov 2015 09:08:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ztyk4-0007pA-NY for qemu-devel@nongnu.org; Wed, 04 Nov 2015 09:08:54 -0500 From: Markus Armbruster References: <1446644927-8764-1-git-send-email-pbonzini@redhat.com> Date: Wed, 04 Nov 2015 15:08:45 +0100 In-Reply-To: <1446644927-8764-1-git-send-email-pbonzini@redhat.com> (Paolo Bonzini's message of "Wed, 4 Nov 2015 14:48:47 +0100") Message-ID: <87lhadluvm.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org, crobinso@redhat.com Paolo Bonzini writes: > Using access() is a time-of-check/time-of-use race condition. It is > okay to use them to provide better error messages, but that is pretty > much it. > > This is not one such case; on the other hand, access() *will* skip > unlink() for a non-existent path, so ignore ENOENT return values from > the unlink() system call. > > Signed-off-by: Paolo Bonzini > --- > util/qemu-sockets.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c > index 9142917..de9145a 100644 > --- a/util/qemu-sockets.c > +++ b/util/qemu-sockets.c > @@ -751,8 +751,7 @@ int unix_listen_opts(QemuOpts *opts, Error **errp) > qemu_opt_set(opts, "path", un.sun_path, &error_abort); > } > > - if ((access(un.sun_path, F_OK) == 0) && > - unlink(un.sun_path) < 0) { > + if (unlink(un.sun_path) < 0 && errno != ENOENT) { > error_setg_errno(errp, errno, > "Failed to unlink socket %s", un.sun_path); > goto err; Reviewed-by: Markus Armbruster