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Wed, 18 Dec 2019 23:12:19 +0000 From: Martin Lau To: Andrii Nakryiko CC: "bpf@vger.kernel.org" , "netdev@vger.kernel.org" , Alexei Starovoitov , "daniel@iogearbox.net" , "andrii.nakryiko@gmail.com" , Kernel Team Subject: Re: [Potential Spoof] [PATCH bpf-next] libbpf: add bpf_link__disconnect() API to preserve underlying BPF resource Thread-Topic: [Potential Spoof] [PATCH bpf-next] libbpf: add bpf_link__disconnect() API to preserve underlying BPF resource Thread-Index: AQHVtfWZJulKll6KC0+Tn29h+sCeNafAhUCA Date: Wed, 18 Dec 2019 23:12:19 +0000 Message-ID: <20191218231215.kzrdnupxs3ybv2zh@kafai-mbp.dhcp.thefacebook.com> References: <20191218225039.2668205-1-andriin@fb.com> In-Reply-To: <20191218225039.2668205-1-andriin@fb.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: CO1PR15CA0112.namprd15.prod.outlook.com (2603:10b6:101:21::32) To MN2PR15MB3213.namprd15.prod.outlook.com (2603:10b6:208:3d::12) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c090:180::afeb] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 338c187b-5fdd-4675-12f4-08d7840fbb1a x-ms-traffictypediagnostic: MN2PR15MB2526: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8273; 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charset="us-ascii" Content-ID: <91EE89DC2267984F841FF20D8AEE51F3@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 338c187b-5fdd-4675-12f4-08d7840fbb1a X-MS-Exchange-CrossTenant-originalarrivaltime: 18 Dec 2019 23:12:19.6537 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: XPHxrBqwD0nWZcSte4rmfRrTQKWQ0NnMiOJmWOwc8yFGH/lSmxlEkzv8Dk96kDCb X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR15MB2526 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-18_08:2019-12-17,2019-12-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 bulkscore=0 priorityscore=1501 spamscore=0 lowpriorityscore=0 mlxlogscore=713 suspectscore=0 phishscore=0 adultscore=0 clxscore=1015 mlxscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912180173 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Dec 18, 2019 at 02:50:39PM -0800, Andrii Nakryiko wrote: > There are cases in which BPF resource (program, map, etc) has to outlive > userspace program that "installed" it in the system in the first place. > When BPF program is attached, libbpf returns bpf_link object, which > is supposed to be destroyed after no longer necessary through > bpf_link__destroy() API. Currently, bpf_link destruction causes both auto= matic > detachment and frees up any resources allocated to for bpf_link in-memory > representation. This is inconvenient for the case described above because= of > coupling of detachment and resource freeing. >=20 > This patch introduces bpf_link__disconnect() API call, which marks bpf_li= nk as > disconnected from its underlying BPF resouces. This means that when bpf_l= ink > is destroyed later, all its memory resources will be freed, but BPF resou= rce > itself won't be detached. >=20 > This design allows to follow strict and resource-leak-free design by defa= ult, > while giving easy and straightforward way for user code to opt for keepin= g BPF > resource attached beyond lifetime of a bpf_link. For some BPF programs (i= .e., > FS-based tracepoints, kprobes, raw tracepoint, etc), user has to make sur= e to > pin BPF program to prevent kernel to automatically detach it on process e= xit. > This should typically be achived by pinning BPF program (or map in some c= ases) > in BPF FS. Thanks for the patch. Acked-by: Martin KaFai Lau