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Message-ID: <c6cab703-87df-4152-a5b0-a0ce31e7f057@moroto.mountain>
Date: Mon, 29 Apr 2024 13:30:28 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
Cc: "dave@...olabs.net" <dave@...olabs.net>,
"jonathan.cameron@...wei.com" <jonathan.cameron@...wei.com>,
"dave.jiang@...el.com" <dave.jiang@...el.com>,
"alison.schofield@...el.com" <alison.schofield@...el.com>,
"vishal.l.verma@...el.com" <vishal.l.verma@...el.com>,
"ira.weiny@...el.com" <ira.weiny@...el.com>,
"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
"linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] cxl/region: Fix potential invalid pointer dereference
On Mon, Apr 29, 2024 at 10:25:35AM +0000, Zhijian Li (Fujitsu) wrote:
> > 3084 mutex_lock(&cxlrd->range_lock);
> > 3085 region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
> > 3086 match_region_by_range);
> > 3087 if (!region_dev) {
> > 3088 cxlr = construct_region(cxlrd, cxled);
> > 3089 region_dev = &cxlr->dev;
> > ^^^^^^^^^^^
> > This is not a dereference, it's just pointer math. In in this case it's
> > the same as saying:
> >
> > region_dev = (void *)cxlr;
>
>
> You are right, a equivalent code could be:
> region_dev = ((char *)cxlr) + offsetof(struct cxl_region, dev);
>
>
Correct. But offsetof() is zero. It's the same math that to_cxl_region()
does.
regards,
dan carpenter
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