linux-kernel - Re: [PATCH] Do not disable driver and bus shutdown hook when class shutdown hook is set.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170809215202.GA21867@obsidianresearch.com>
Date:   Wed, 9 Aug 2017 15:52:02 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Michal Suchanek <msuchanek@...e.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net
Subject: Re: [PATCH] Do not disable driver and bus shutdown hook when class
 shutdown hook is set.

On Wed, Aug 09, 2017 at 11:34:20PM +0200, Michal Suchanek wrote:
> Disabling the driver hook by setting class hook is totally sound design
> not prone to error as evidenced by the single implementation of the
> class hook.

It was done this was for consistency, if you look at the full code:

                if (dev->class && dev->class->shutdown) {
                        if (initcall_debug)
                                dev_info(dev, "shutdown\n");
                        dev->class->shutdown(dev);
                } else if (dev->bus && dev->bus->shutdown) {
                        if (initcall_debug)
                                dev_info(dev, "shutdown\n");
                        dev->bus->shutdown(dev);
                } else if (dev->driver && dev->driver->shutdown) {
                        if (initcall_debug)
                                dev_info(dev, "shutdown\n");
                        dev->driver->shutdown(dev);
                }

The bus disables the driver callback, on the expectation that the bus
implementation will do it.

Existing bus implementations do properly chain to driver shutdown (eg
look at mmc_bus_shutdown) and it appears to have been written like
this so that the bus can insert code before and after calling the
driver shutdown.

Making class act differently from bus seems very confusing, IHMO,
which why the TPM patch was written to follow the existing pattern.

Jason