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Fri, 29 May 2026 15:25:27 +0000 Date: Fri, 29 May 2026 08:25:23 -0700 From: Alison Schofield To: Li Ming CC: , , , , , , , Subject: Re: [PATCH v3 1/1] cxl/region: Fix out-of-bounds access in cxl_cancel_auto_attach() Message-ID: References: <20260529132533.1144383-1-ming.li@zohomail.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260529132533.1144383-1-ming.li@zohomail.com> X-ClientProxiedBy: BY1P220CA0010.NAMP220.PROD.OUTLOOK.COM (2603:10b6:a03:59d::12) To DS4PPF0BAC23327.namprd11.prod.outlook.com (2603:10b6:f:fc02::9) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS4PPF0BAC23327:EE_|CYXPR11MB8710:EE_ X-MS-Office365-Filtering-Correlation-Id: 84adf38f-cee1-4d15-b004-08debd9682f1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|22082099003|6133799003|18002099003|56012099006|11063799006; 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However, cxled->pos can be set to negative errno > in cxl_region_sort_targets() if cxl_calc_interleave_pos() fails. This > causes the driver to use a negative index to access p->targets[], > resulting in out-of-bounds access. > > Fix it by walking p->targets[] instead of using cxled->pos directly. > > Fixes: 87805c32e6ad ("cxl/region: Fix use-after-free from auto assembly failure") > Signed-off-by: Li Ming Reviewed-by: Alison Schofield > --- > Changes from v2: > - Revert "Fix potential 'hole' issue." changes. (Alison) > > Changes from v1: > - Update commit log. (Dave) > - Update comment in cxl_region_sort_targets(). (Dave) > - Fix potential 'hole' issue. (Alison & Sashiko review) > --- > drivers/cxl/core/region.c | 40 +++++++++++++++++++-------------------- > 1 file changed, 19 insertions(+), 21 deletions(-) > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > index e50dc716d4e8..eb96cb3cae83 100644 > --- a/drivers/cxl/core/region.c > +++ b/drivers/cxl/core/region.c > @@ -2011,8 +2011,9 @@ static int cxl_region_sort_targets(struct cxl_region *cxlr) > cxled->pos = cxl_calc_interleave_pos(cxled, &cxlr->hpa_range); > /* > * Record that sorting failed, but still continue to calc > - * cxled->pos so that follow-on code paths can reliably > - * do p->targets[cxled->pos] to self-reference their entry. > + * cxled->pos so that cxl_calc_interleave_pos() emits its > + * dev_dbg() for every member. which is useful for auto > + * discovery debug. > */ > if (cxled->pos < 0) > rc = -ENXIO; > @@ -2202,18 +2203,30 @@ static int cxl_region_attach(struct cxl_region *cxlr, > return 0; > } > > -static int cxl_region_by_target(struct device *dev, const void *data) > +static int cxl_region_remove_target(struct device *dev, void *data) > { > - const struct cxl_endpoint_decoder *cxled = data; > + struct cxl_endpoint_decoder *cxled = data; > struct cxl_region_params *p; > struct cxl_region *cxlr; > + int i; > > if (!is_cxl_region(dev)) > return 0; > > cxlr = to_cxl_region(dev); > p = &cxlr->params; > - return p->targets[cxled->pos] == cxled; > + for (i = 0; i < p->nr_targets; i++) { > + if (p->targets[i] == cxled) { > + p->nr_targets--; > + cxled->state = CXL_DECODER_STATE_AUTO; > + cxled->pos = -1; > + p->targets[i] = NULL; > + > + return 1; > + } > + } > + > + return 0; > } > > /* > @@ -2222,25 +2235,10 @@ static int cxl_region_by_target(struct device *dev, const void *data) > */ > static void cxl_cancel_auto_attach(struct cxl_endpoint_decoder *cxled) > { > - struct cxl_region_params *p; > - struct cxl_region *cxlr; > - int pos = cxled->pos; > - > if (cxled->state != CXL_DECODER_STATE_AUTO_STAGED) > return; > > - struct device *dev __free(put_device) = > - bus_find_device(&cxl_bus_type, NULL, cxled, cxl_region_by_target); > - if (!dev) > - return; > - > - cxlr = to_cxl_region(dev); > - p = &cxlr->params; > - > - p->nr_targets--; > - cxled->state = CXL_DECODER_STATE_AUTO; > - cxled->pos = -1; > - p->targets[pos] = NULL; > + bus_for_each_dev(&cxl_bus_type, NULL, cxled, cxl_region_remove_target); > } > > static struct cxl_region * > -- > 2.43.0 >