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

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Date: Mon, 24 Jun 2024 09:18:41 -0700
From: Davidlohr Bueso <dave@...olabs.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>,
	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, 18 Jun 2024, 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().

Reviewed-by: Davidlohr Bueso <dave@...olabs.net>