linux-kernel - Re: [PATCH 3/3] platform/x86: intel_scu

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: <ZPCenoPp/SDesUek@smile.fi.intel.com>
Date:   Thu, 31 Aug 2023 17:07:26 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        platform-driver-x86@...r.kernel.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Prashant Malani <pmalani@...omium.org>
Subject: Re: [PATCH 3/3] platform/x86: intel_scu_ipc: Fail IPC send if still
 busy

On Wed, Aug 30, 2023 at 06:14:03PM -0700, Stephen Boyd wrote:
> It's possible for interrupts to get significantly delayed to the point
> that callers of intel_scu_ipc_dev_command() and friends can call the
> function once, hit a timeout, and call it again while the interrupt
> still hasn't been processed. This driver will get seriously confused if
> the interrupt is finally processed after the second IPC has been sent
> with ipc_command(). It won't know which IPC has been completed. This
> could be quite disastrous if calling code assumes something has happened
> upon return from intel_scu_ipc_dev_simple_command() when it actually
> hasn't.
> 
> Let's avoid this scenario by simply returning -EBUSY in this case.
> Hopefully higher layers will know to back off or fail gracefully when
> this happens. It's all highly unlikely anyway, but it's better to be
> correct here as we have no way to know which IPC the status register is
> telling us about if we send a second IPC while the previous IPC is still
> processing.

> +static bool intel_scu_ipc_busy(struct intel_scu_ipc_dev *scu)

static int ?

> +{
> +	u8 status;
> +
> +	status = ipc_read_status(scu);
> +	if (status & IPC_STATUS_BUSY) {

> +		dev_err(&scu->dev, "device is busy\n");

1. Wouldn't it exaggerate the logs? Shouldn't be rate limited?
2. OTOH if we return -EBUSY directly from here, do we need this at all?

> +		return true;
> +	}
> +
> +	return false;
> +}

-- 
With Best Regards,
Andy Shevchenko