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

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Date:   Tue, 4 Aug 2020 07:33:15 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Evgeny Novikov <novikov@...ras.ru>,
        Jean Delvare <jdelvare@...e.com>
Cc:     linux-hwmon@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: hwmon: (sis5595) potential null pointer dereference in probe

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.

> 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.

Guenter