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V" , Davidlohr Bueso , Vishal Verma , Ira Weiny Subject: Re: [PATCH v3 1/3] cxl/region: Fix a race condition in memory hotplug notifier Message-ID: References: <20240618084639.1419629-1-ying.huang@intel.com> <20240618084639.1419629-2-ying.huang@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240618084639.1419629-2-ying.huang@intel.com> 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" > Cc: Dan Williams > Cc: Alison Schofield > Cc: Andrew Morton > Cc: Jonathan Cameron > Cc: Dave Jiang > Cc: Bharata B Rao > Cc: Alistair Popple > Cc: Aneesh Kumar K.V > Cc: Davidlohr Bueso > Cc: Vishal Verma > Cc: Ira Weiny > --- Reviewed-by: Fan Ni > drivers/cxl/core/region.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index 3c2b6144be23..51aeef2c012c 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -2304,14 +2304,25 @@ static bool cxl_region_update_coordinates(struct cxl_region *cxlr, int nid) > return true; > } > > +static int cxl_region_nid(struct cxl_region *cxlr) > +{ > + struct cxl_region_params *p = &cxlr->params; > + struct cxl_endpoint_decoder *cxled; > + struct cxl_decoder *cxld; > + > + guard(rwsem_read)(&cxl_region_rwsem); > + cxled = p->targets[0]; > + if (!cxled) > + return NUMA_NO_NODE; > + cxld = &cxled->cxld; > + return phys_to_target_node(cxld->hpa_range.start); > +} > + > static int cxl_region_perf_attrs_callback(struct notifier_block *nb, > unsigned long action, void *arg) > { > struct cxl_region *cxlr = container_of(nb, struct cxl_region, > memory_notifier); > - struct cxl_region_params *p = &cxlr->params; > - struct cxl_endpoint_decoder *cxled = p->targets[0]; > - struct cxl_decoder *cxld = &cxled->cxld; > struct memory_notify *mnb = arg; > int nid = mnb->status_change_nid; > int region_nid; > @@ -2319,7 +2330,7 @@ static int cxl_region_perf_attrs_callback(struct notifier_block *nb, > if (nid == NUMA_NO_NODE || action != MEM_ONLINE) > return NOTIFY_DONE; > > - region_nid = phys_to_target_node(cxld->hpa_range.start); > + region_nid = cxl_region_nid(cxlr); > if (nid != region_nid) > return NOTIFY_DONE; > > -- > 2.39.2 >