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Tue, 5 May 2020 19:05:15 +0000 Date: Tue, 5 May 2020 12:05:12 -0700 From: Martin KaFai Lau To: John Fastabend CC: , , , , Subject: Re: [PATCH 2/2] bpf: sockmap, bpf_tcp_ingress needs to subtract bytes from sg.size Message-ID: <20200505190512.5pxrhf3mzh2cj65b@kafai-mbp> References: <158861271707.14306.15853815339036099229.stgit@john-Precision-5820-Tower> <158861290407.14306.5327773422227552482.stgit@john-Precision-5820-Tower> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158861290407.14306.5327773422227552482.stgit@john-Precision-5820-Tower> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: BYAPR01CA0070.prod.exchangelabs.com (2603:10b6:a03:94::47) To MW3PR15MB4044.namprd15.prod.outlook.com (2603:10b6:303:4b::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp (2620:10d:c090:400::5:3100) by BYAPR01CA0070.prod.exchangelabs.com (2603:10b6:a03:94::47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2979.27 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 251838a0-a02a-4a29-bb19-08d7f1273e2e X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2020 19:05:14.8649 (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: CkyJ/8irJfijWL4JGdXsHi6CnTfhiBS9UobXQ9r86YssSJF0J3Ih06I6H3YXF2Jp X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW3PR15MB3946 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-05-05_10:2020-05-04,2020-05-05 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=558 priorityscore=1501 impostorscore=0 lowpriorityscore=0 phishscore=0 adultscore=0 bulkscore=0 spamscore=0 malwarescore=0 suspectscore=2 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050145 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, May 04, 2020 at 10:21:44AM -0700, John Fastabend wrote: > In bpf_tcp_ingress we used apply_bytes to subtract bytes from sg.size > which is used to track total bytes in a message. But this is not > correct because apply_bytes is itself modified in the main loop doing > the mem_charge. > > Then at the end of this we have sg.size incorrectly set and out of > sync with actual sk values. Then we can get a splat if we try to > cork the data later and again try to redirect the msg to ingress. To > fix instead of trying to track msg.size do the easy thing and include > it as part of the sk_msg_xfer logic so that when the msg is moved the > sg.size is always correct. > > To reproduce the below users will need ingress + cork and hit an > error path that will then try to 'free' the skmsg. > > [ 173.699981] BUG: KASAN: null-ptr-deref in sk_msg_free_elem+0xdd/0x120 > [ 173.699987] Read of size 8 at addr 0000000000000008 by task test_sockmap/5317 > > [ 173.700000] CPU: 2 PID: 5317 Comm: test_sockmap Tainted: G I 5.7.0-rc1+ #43 > [ 173.700005] Hardware name: Dell Inc. Precision 5820 Tower/002KVM, BIOS 1.9.2 01/24/2019 > [ 173.700009] Call Trace: > [ 173.700021] dump_stack+0x8e/0xcb > [ 173.700029] ? sk_msg_free_elem+0xdd/0x120 > [ 173.700034] ? sk_msg_free_elem+0xdd/0x120 > [ 173.700042] __kasan_report+0x102/0x15f > [ 173.700052] ? sk_msg_free_elem+0xdd/0x120 > [ 173.700060] kasan_report+0x32/0x50 > [ 173.700070] sk_msg_free_elem+0xdd/0x120 > [ 173.700080] __sk_msg_free+0x87/0x150 > [ 173.700094] tcp_bpf_send_verdict+0x179/0x4f0 > [ 173.700109] tcp_bpf_sendpage+0x3ce/0x5d0 > > Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface") > Signed-off-by: John Fastabend Acked-by: Martin KaFai Lau