linux-kernel - Re: regmap: mmio: lack of runtime

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: <CA+ASDXO-61=D0DM+d4dNCbEYV3omroFbbFao3YrUPOYy+7AJUg@mail.gmail.com>
Date:   Fri, 4 Feb 2022 12:05:07 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Peng Fan <peng.fan@....com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "S.j. Wang" <shengjiu.wang@....com>
Subject: Re: regmap: mmio: lack of runtime_pm support for debugfs

After a bit more thinking:

On Fri, Feb 4, 2022 at 11:21 AM Brian Norris <briannorris@...omium.org> wrote:
> Anyway, I'll probably just go with precious_reg() as suggested above.

Unfortunately, precious_reg() wouldn't be quite safe either -- we
could do a single check for pm_runtime_active(), but we have no way of
knowing (guaranteeing) that it will remain active throughout the
remainder of the debugfs operation. For all we know, some other actor
could be *just* finishing with (and PM-suspending) our domain
immediately after the check. And we can't grab a reference, because we
don't have a callback for balancing that back out.

If I really want to solve this, I might have to go with adding a
debugfs-specific runtime_pm flag, and (to avoid too many side effects)
use that with pm_runtime_get_if_active() in regmap-debugfs.c.

Brian