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Tue, 7 Jul 2020 18:32:32 +0000 Date: Tue, 7 Jul 2020 11:32:31 -0700 From: Martin KaFai Lau To: James Chapman CC: , Subject: Re: bpf's usage of sk_user_data Message-ID: <20200707183231.hfxtzfpfcf7g3jwp@kafai-mbp> References: <20200707093730.GC21324@katalix.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200707093730.GC21324@katalix.com> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: BY5PR20CA0006.namprd20.prod.outlook.com (2603:10b6:a03:1f4::19) To BY5PR15MB3571.namprd15.prod.outlook.com (2603:10b6:a03:1f6::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp (2620:10d:c090:400::5:6c3d) by BY5PR20CA0006.namprd20.prod.outlook.com (2603:10b6:a03:1f4::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3174.20 via Frontend Transport; Tue, 7 Jul 2020 18:32:32 +0000 X-Originating-IP: [2620:10d:c090:400::5:6c3d] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: a30dd510-b7cf-4178-1d09-08d822a41c8d X-MS-TrafficTypeDiagnostic: BYAPR15MB2824: X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:549; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: a30dd510-b7cf-4178-1d09-08d822a41c8d X-MS-Exchange-CrossTenant-AuthSource: BY5PR15MB3571.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2020 18:32:32.3415 (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: H8iij9jCoW+hDY/KV7JANR5YLmfF5VdvW/wL/AGE4LTjHpx0pg0LF6ZDG5mwp+PU X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2824 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-07_10:2020-07-07,2020-07-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 bulkscore=0 clxscore=1015 impostorscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 mlxlogscore=999 spamscore=0 cotscore=-2147483648 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007070124 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Jul 07, 2020 at 10:37:30AM +0100, James Chapman wrote: > I'm investigating a crash found by syzbot which turns out to be caused > by bpf_sk_reuseport_detach assuming ownership of sk_user_data in the > UDP socket destroy path and corrupts metadata of a UDP socket user (l2tp). > > Here's the syzbot report: > https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3D9f092552ba9a5efca5df&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=VQnoQ7LvghIj0gVEaiQSUw&m=p6aRc9baiGL-RnWqirYKbVXROY5Qc1x4T5-HWjxEp0g&s=mPnfVsw-U-eTV_dezjfYUahIbSiW8wEg4jC44e-mris&e= > > I submitted a patch to l2tp to workaround this by having l2tp refuse > to use a UDP socket with SO_REUSEPORT set. But this isn't the right > fix. Can BPF be changed to store its metadata elsewhere such that > other socket users which use sk_user_data can co-exist with BPF? > > The email thread discussing this is at: > https://lore.kernel.org/netdev/20200706.124536.774178117550894539.davem@davemloft.net/ I have replied on the original thread. Thanks.