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[209.132.180.67]) by mx.google.com with ESMTP id v129-v6si30693154pfc.330.2018.07.15.02.06.21; Sun, 15 Jul 2018 02:06:36 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726224AbeGOJ2C (ORCPT + 99 others); Sun, 15 Jul 2018 05:28:02 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33994 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726032AbeGOJ2C (ORCPT ); Sun, 15 Jul 2018 05:28:02 -0400 Received: from localhost (LFbn-1-12247-202.w90-92.abo.wanadoo.fr [90.92.61.202]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id B70DDA95; Sun, 15 Jul 2018 09:05:46 +0000 (UTC) Date: Sun, 15 Jul 2018 11:05:44 +0200 From: Greg Kroah-Hartman To: Todd Poynor Cc: Rob Springer , John Joseph , Ben Chan , devel@driverdev.osuosl.org, Zhongze Hu , linux-kernel@vger.kernel.org, Simon Que , Guenter Roeck , Todd Poynor , Dmitry Torokhov Subject: Re: [PATCH 11/18] staging: gasket: always allow root open for write Message-ID: <20180715090544.GC23333@kroah.com> References: <20180714055816.223754-1-toddpoynor@gmail.com> <20180714055816.223754-12-toddpoynor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180714055816.223754-12-toddpoynor@gmail.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 13, 2018 at 10:58:09PM -0700, Todd Poynor wrote: > From: Todd Poynor > > Always allow root to open device for writing. > > Drop special-casing of ioctl permissions for root vs. owner. > > Reported-by: Dmitry Torokhov > Signed-off-by: Zhongze Hu > Signed-off-by: Todd Poynor > --- > drivers/staging/gasket/apex_driver.c | 9 +++------ > drivers/staging/gasket/gasket_core.c | 8 +++++--- > drivers/staging/gasket/gasket_ioctl.c | 15 ++++++--------- > 3 files changed, 14 insertions(+), 18 deletions(-) > > diff --git a/drivers/staging/gasket/apex_driver.c b/drivers/staging/gasket/apex_driver.c > index b1318482ba65..ffe11d8168ea 100644 > --- a/drivers/staging/gasket/apex_driver.c > +++ b/drivers/staging/gasket/apex_driver.c > @@ -644,13 +644,10 @@ static bool is_gcb_in_reset(struct gasket_dev *gasket_dev) > static uint apex_ioctl_check_permissions(struct file *filp, uint cmd) > { > struct gasket_dev *gasket_dev = filp->private_data; > - int root = capable(CAP_SYS_ADMIN); > - int is_owner = gasket_dev->dev_info.ownership.is_owned && > - current->tgid == gasket_dev->dev_info.ownership.owner; > + fmode_t write; > > - if (root || is_owner) > - return 1; > - return 0; > + write = filp->f_mode & FMODE_WRITE; Ok, this is insane. You don't change, or check, the permissions on a file handle while it is already open, as you only check the permissions on OPEN, not on WRITE. See the recent rant from Linus on the linux-api list for yet-another-long-threaad in which he explains this. So this whole ioctl can just be removed, it is totally crazy and wrong and should just be removed. Want me to go remove it right now? thanks, greg k-h