linux-kernel - Re: hwmon: (sis5595) potential null pointer dereference in probe

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Date:   Tue, 04 Aug 2020 17:48:48 +0300
From:   Evgeny Novikov <novikov@...ras.ru>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>
Cc:     "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        ldv-project-org <ldv-project@...uxtesting.org>
Subject: Re: hwmon: (sis5595) potential null pointer dereference in probe

04.08.2020, 17:33, "Guenter Roeck" <linux@...ck-us.net>:
> On 8/4/20 4:50 AM, Evgeny Novikov wrote:
>>  sis5595_pci_probe() registers platform driver callbacks and just then
>>  initializes global pointer variable s_bridge. sis5595_probe() may
>>  dereference it before this happens that can result in null pointer
>>  dereference.
>
> sis5595_probe() is only called after the device is registered,
> which happens in sis5595_device_add() after s_bridge is set. This is
> a southbridge, so there won't be any hot insertion/removal events.
>

Thank you for this hint. We need to tune our models appropriately.

>>  We can not swap registration of platform driver callbacks with
>>  initialization of s_bridge since sm_sis5595_exit() assumes the
>>  current order. Perhaps it has sense to implement a pci_driver.remove
>>  callback that will take care about deregistration of platform driver
>>  callbacks.
>
> Agreed regarding the remove function. However, given the age of the chip,
> I'd rather remove the driver than spending time on cleanup efforts.
> This looks like a perfect candidate for depreciation.
>

This is completely up to you. Anyway the driver does not have the bug.

Best regards,
Evgeny

> Guenter