linux-kernel - Re: [PATCH v3 1/3] cxl/region: Fix a race condition in memory hotplug notifier

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Message-ID: <Zp++y0KOrWs6NKrW@devbig133.nha1.facebook.com>
Date: Tue, 23 Jul 2024 07:31:39 -0700
From: Gregory Price <gourry@...rry.net>
To: Huang Ying <ying.huang@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alison Schofield <alison.schofield@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Bharata B Rao <bharata@....com>,
	Alistair Popple <apopple@...dia.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH v3 1/3] cxl/region: Fix a race condition in memory
 hotplug notifier

On Tue, Jun 18, 2024 at 04:46:37PM +0800, Huang Ying wrote:
> In the memory hotplug notifier function of the CXL region,
> cxl_region_perf_attrs_callback(), the node ID is obtained by checking
> the host address range of the region. However, the address range
> information is not available when the region is registered in
> devm_cxl_add_region(). Additionally, this information may be removed
> or added under the protection of cxl_region_rwsem during runtime. If
> the memory notifier is called for nodes other than that backed by the
> region, a race condition may occur, potentially leading to a NULL
> dereference or an invalid address range.
> 
> The race condition is addressed by checking the availability of the
> address range information under the protection of cxl_region_rwsem. To
> enhance code readability and use guard(), the relevant code has been
> moved into a newly added function: cxl_region_nid().
> 
> Fixes: 067353a46d8c ("cxl/region: Add memory hotplug notifier for cxl region")
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>

Good catch

Reviewed-by: Gregory Price <gourry@...rry.net>