Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756585AbaDVNxA (ORCPT ); Tue, 22 Apr 2014 09:53:00 -0400 Received: from mail-lb0-f171.google.com ([209.85.217.171]:38817 "EHLO mail-lb0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756289AbaDVNwx (ORCPT ); Tue, 22 Apr 2014 09:52:53 -0400 MIME-Version: 1.0 Reply-To: mtk.manpages@gmail.com In-Reply-To: References: <1397940833-6386-1-git-send-email-xypron.glpk@gmx.de> <20140422134044.GE366@quack.suse.cz> From: "Michael Kerrisk (man-pages)" Date: Tue, 22 Apr 2014 15:52:32 +0200 Message-ID: Subject: Re: [PATCH 1/1] fanotify: check permissions when creating file descriptor To: Jan Kara Cc: Heinrich Schuchardt , Eric Paris , lkml Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 22, 2014 at 3:50 PM, Michael Kerrisk (man-pages) wrote: > On Tue, Apr 22, 2014 at 3:40 PM, Jan Kara wrote: >> On Sat 19-04-14 22:53:53, Heinrich Schuchardt wrote: >>> When monitoring a directory or a mount with the fanotify API >>> the call to fanotify_init checks, >>> * the process has cap_sys_admin capability >>> >>> The call to fanotify_mark checks, >>> * the process has read authorization for directory or mount >>> >>> A directory or mount may contain files for which the process >>> has no read or write authorization. >>> Yet when reading from the fanotify file descriptor, structures >>> fanotify_event_metadata are returned, which contain a file >>> descriptor for these files, and will allow to read or write. >>> >>> The patch adds an authorization check for read and write >>> permission. In case of missing permission, reading from the >>> fanotify file descriptor returns EACCES. >> OK, am I right you are concerned about a situation where fanotify group >> descriptor is passed to an unpriviledged process which handles all the >> incoming events? I'm asking because the permission checking can be >> relatively expensive (think of acls) so we better do it for a reason. >> I'd prefer to hear from Eric what the original intention regarding >> permissions was... > > If I understand correctly, passing to an unprivileged process is the sorry: s/is the/is not the/ -- 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/