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Sun, 3 Nov 2019 00:25:44 +0000 From: Chaitanya Kulkarni To: Ming Lei , Jens Axboe CC: "linux-block@vger.kernel.org" Subject: Re: [PATCH] blk-mq: avoid sysfs buffer overflow by too many CPU cores Thread-Topic: [PATCH] blk-mq: avoid sysfs buffer overflow by too many CPU cores Thread-Index: AQHVkVPqDb9QIWc6hE6kE3ixbLET/w== Date: Sun, 3 Nov 2019 00:25:44 +0000 Message-ID: References: <20191102080215.20223-1-ming.lei@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Chaitanya.Kulkarni@wdc.com; x-originating-ip: [199.255.45.62] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 7fa78424-8b77-44b4-f4f2-08d75ff45db4 x-ms-traffictypediagnostic: BYAPR04MB6133: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:3383; x-forefront-prvs: 0210479ED8 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(4636009)(396003)(39860400002)(366004)(136003)(346002)(376002)(199004)(189003)(3846002)(2906002)(6116002)(476003)(66446008)(66476007)(26005)(52536014)(7696005)(74316002)(305945005)(7736002)(33656002)(76176011)(8676002)(256004)(8936002)(102836004)(6506007)(86362001)(5660300002)(186003)(71200400001)(478600001)(71190400001)(6436002)(81166006)(6246003)(66556008)(64756008)(66066001)(55016002)(9686003)(229853002)(99286004)(4326008)(446003)(76116006)(486006)(4744005)(81156014)(25786009)(14454004)(66946007)(110136005)(53546011)(316002);DIR:OUT;SFP:1102;SCL:1;SRVR:BYAPR04MB6133;H:BYAPR04MB5749.namprd04.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: TiOX4M9199KlJAuCRuihg4JKE01ETBAVYy/LSjNn/Uw6++4SzxwGrlJJywkxqvnb54x2Cc+BJ8CDpLs6WXlEQOAd+ZDeLJutSRYc5QkQT/73CSXR96WWJXd9C9l513TUitXdKZNgzWNmhfK/v2oFCZkcTH1K0jPysP8M/UFjYF3c5NUmjayfvEXqJtLZX9+wqjd6RRX53BI480cpW9nINk8oClb3u3hpLCSWcyJu+sSndx2LHKiudFsbVW3pt5+qM8sXS4bWAm9jRofJWg+L91T/uatIKiR7AWO8MJa6u0COT889vKWUHTb51xrTaSmLYx/nmcKOGSq38Rnb77sHodsnncg34mIY8FqstPHl1loWSuOo2hWYPc4Gh2zjk25YiiY77YjrLBcQymIzzPEYI/nW0PbJZ4Nq6Lo2Fx7ykAzEDZUpXgwSe4I1r+9qXV6y x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7fa78424-8b77-44b4-f4f2-08d75ff45db4 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Nov 2019 00:25:44.2245 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: qs+bg9bjRi5xNmhmt40jSWUtWOhjY1avXuOVxMXmdtyC0h9E1lZDb9jBltuE3GwhdFs/eVBnX2dGWQHqwC3i0jdwMmGJF4XmBFGjJpDA1m8= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR04MB6133 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Ming,=0A= =0A= On 11/02/2019 01:02 AM, Ming Lei wrote:=0A= > It is reported that sysfs buffer overflow can be triggered in case=0A= > of too many CPU cores(>841 on 4K PAGE_SIZE) when showing CPUs of=0A= > hctx via/sys/block/$DEV/mq/$N/cpu_list.=0A= >=0A= > So use snprintf for avoiding the potential buffer overflow.=0A= >=0A= > This version doesn't change the attribute format, and simply stop=0A= > to show CPU number if the buffer is to be overflow.=0A= =0A= Does it make sense to also add a print or WARN_ON in case of overflow ?=0A=