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Mon, 9 Mar 2020 05:39:56 +0000 Subject: Re: [RFC PATCH 2/4] bpf: verifier, do explicit u32 bounds tracking To: John Fastabend , , CC: , References: <158353965971.3451.14666851223845760316.stgit@ubuntu3-kvm2> <158353986285.3451.6986018098665897886.stgit@ubuntu3-kvm2> <5e62e95b61bdf_5f672ade5903a5b83c@john-XPS-13-9370.notmuch> From: Yonghong Song Message-ID: Date: Sun, 8 Mar 2020 22:39:52 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 In-Reply-To: <5e62e95b61bdf_5f672ade5903a5b83c@john-XPS-13-9370.notmuch> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MWHPR2201CA0055.namprd22.prod.outlook.com (2603:10b6:301:16::29) To DM6PR15MB3001.namprd15.prod.outlook.com (2603:10b6:5:13c::16) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from MacBook-Pro-52.local (2620:10d:c090:400::5:23) by MWHPR2201CA0055.namprd22.prod.outlook.com (2603:10b6:301:16::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2793.17 via Frontend Transport; Mon, 9 Mar 2020 05:39:54 +0000 X-Originating-IP: [2620:10d:c090:400::5:23] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 30ee1f78-b49b-4e96-0d65-08d7c3ec4c3f X-MS-TrafficTypeDiagnostic: DM6PR15MB3799: X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-Forefront-PRVS: 0337AFFE9A X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(366004)(396003)(39850400004)(136003)(346002)(376002)(199004)(189003)(6512007)(6486002)(4326008)(2906002)(52116002)(53546011)(6506007)(2616005)(16526019)(316002)(66476007)(66946007)(31686004)(66556008)(5660300002)(478600001)(81156014)(36756003)(81166006)(8676002)(31696002)(86362001)(8936002)(186003);DIR:OUT;SFP:1102;SCL:1;SRVR:DM6PR15MB3799;H:DM6PR15MB3001.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; Received-SPF: None (protection.outlook.com: fb.com does not designate permitted sender hosts) X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: HJWSIkc6hMH7aIFHo4NWykLhsfZk6jtWrcJr8artVZUdMXvTNlCm7BRFNEz6cGLJpw+6OdUFwrO2TNTYHM9ZmhnSvHwRaobB6QfOCb6Yx9cW9r+Gdfmuf1dyMpQOZcumMRLlMuaS+jNBWUyswnU32IpjO0PN6zPDPsVfX3XBqLIfgvfXD6TibrHXeRm2t7zzrWhxVlbO1OOLLhTPc0mX2wRnsVDOFNY1g0eaFMFmzh6Wrx4BnJ0TJVQEcTOsvAP88sQVAl+XOWUeUiXQGDfRN3R9Zm5T4Q6PaMywM3hlhBmg1imuaxFiyQmYJ0ENyIlSefDNbiAS7qjxe1UxryfIrb3fFfZUvEi7FllpPWKe/woiG9glp1+djOxr1xUtozScMAa0Fg11yhsykl597VvSwqGXPj5UYE1e/6BGu5qXoCrZH+aQNPP8UEKEfrHegOzn X-MS-Exchange-AntiSpam-MessageData: ByxrvEQplcxfQYRmQJ7h63qWixmrddpVzZKhMDuX4/UCkIB3RaYI3Uj70bYmcRJX2RP73GvIsyg6J++oGeoMql7NzO33dSZcpEG3Q+5SQf24RPlirYMUVhN1xcu9kTNMoaZ38QHTGZ/2a09IH2reD1EtJ90Ozu3/t1pCbj7AWEk= X-MS-Exchange-CrossTenant-Network-Message-Id: 30ee1f78-b49b-4e96-0d65-08d7c3ec4c3f X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Mar 2020 05:39:56.5107 (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: jZ+vmYoYfM8M9trwdIHG9w2SvYeapPAc3Oo0TISU4T3gZU5/dq2pjacwag3D+3w0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR15MB3799 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-03-09_01:2020-03-06,2020-03-09 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 malwarescore=0 impostorscore=0 phishscore=0 mlxlogscore=999 suspectscore=0 priorityscore=1501 mlxscore=0 adultscore=0 spamscore=0 lowpriorityscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003090041 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 3/6/20 4:22 PM, John Fastabend wrote: > John Fastabend wrote: >> It is not possible for the current verifier to track u32 alu ops and jmps >> correctly. This can result in the verifier aborting with errors even though >> the program should be verifiable. Cilium code base has hit this but worked >> around it by changing int variables to u64 variables and marking a few >> things volatile. It would be better to avoid these tricks. > > Quick bit of clarification, originally I tried to just track u32 hence > the title and above u32 reference. After runnning some programs I realized > this wasn't really enough to handle all cases so I added the signed 32-bit > bounds tracker. If I missed some spots in the descriptions that was just > because I missed it in the proof reading here. u32 above should be 32-bit > subreg. > > I also forgot to give Yonhong credit. Sorry Yonghong! The original alu ops > tracking patch came from him. John, thanks for working on this! Hopefully this will resolve tricky 32bit subreg tracking issues. I will look at the RFC in the next couple of days!