linux-kernel - Re: suspected null-pointer-reference problem for to

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Message-ID: <YXgtxXNIyJ8+G4Oy@smile.fi.intel.com>
Date:   Tue, 26 Oct 2021 19:33:09 +0300
From:   "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     YE Chengfeng <cyeaa@...nect.ust.hk>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: suspected null-pointer-reference problem for to_swnode

On Tue, Oct 26, 2021 at 06:11:57PM +0300, Sakari Ailus wrote:
> On Mon, Oct 25, 2021 at 07:40:55PM +0300, andriy.shevchenko@...ux.intel.com wrote:
> > On Mon, Oct 25, 2021 at 02:03:51PM +0000, YE Chengfeng wrote:
> > > Hi, 
> > > 
> > > https://github.com/torvalds/linux/blob/master/drivers/base/swnode.c#L405
> > > 
> > > We notice that the return pointer of to_swnode is null check in some case, while in some case is not. For example, at line 416, the return pointer is null-check, but in line 405 is not. We want to know whether it would be a potential null pointer dereference problem, in the case that null-check is missing.
> > > 
> > > This problem is detected by our experimental static analysis tool, we are not familiar with the source code and it could just be a false positive. We send this email in case this is a real problem. Would you like to spare some time to have a look at it?
> > 
> > Thank you for the interest to our code!
> > 
> > Line #405 refers to software node operations and it means it won't be ever
> > called if there is no swnode behind it, means it's backed with properties.
> > If you think it will be a NULL pointer there, please describe in detail
> > (with a traceback included) when and how it happens, because such bugs are
> > serious.
> > 
> > Line #416 refers to the same stage when options are defined and we know we
> > have been called against swnode. Seems to me like a dead code brought from
> > day 1 by the commit bc0500c1e43d ("device property: Add fwnode_get_name
> > for returning the name of a node").
> > 
> > Sakari?
> 
> Yeah, the check could be removed.

I have just sent a patch.

-- 
With Best Regards,
Andy Shevchenko