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Fri, 10 Apr 2020 23:47:39 +0000 Subject: Re: [RFC PATCH bpf-next 05/16] bpf: create file or anonymous dumpers To: Andrii Nakryiko CC: Alexei Starovoitov , Andrii Nakryiko , bpf , Martin KaFai Lau , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team References: <20200408232520.2675265-1-yhs@fb.com> <20200408232526.2675664-1-yhs@fb.com> <20200410030017.errh35srmbmd7uk5@ast-mbp.dhcp.thefacebook.com> From: Yonghong Song Message-ID: <2d941e43-72de-b641-22b8-b9ec970ccf52@fb.com> Date: Fri, 10 Apr 2020 16:47:36 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MWHPR15CA0038.namprd15.prod.outlook.com (2603:10b6:300:ad::24) To MW3PR15MB3883.namprd15.prod.outlook.com (2603:10b6:303:51::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from MacBook-Pro-52.local (2620:10d:c090:400::5:e0e4) by MWHPR15CA0038.namprd15.prod.outlook.com (2603:10b6:300:ad::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2900.15 via Frontend Transport; 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X-Microsoft-Antispam-Message-Info: nCjCACPMsJvA5J95Lmctrv4Z1siN4HutE4NMVi9qHQM32WN9O5SpPzEcns0h2B4HrEPZxZVlpUz0G/M+TZbvO90TK7sjDS7dkt7p8DQwsKI/mhLZCRqthw7IsRB0wzgDBNmRagkJwM3yBqG+1lvXyDgTfVLtdqvlCAX/DzTFBsdNVWGf9EcpH6qr6thh+bKxKcPzqU/0B6eQQ6Osrym1g1Hj8/jao+2jmR2msHGdWPDfQ0AguRdMmo/5npDDjELaq1gjy0F+6nhPEySniqtbUFULHexc0ZdKzvkBYHGX+rK66qHE+YjQCI3MMZ5UtOjybBvQ0PNEBXvV6yCxvXYpSrd3NXXdKERkLsHnfppYBKXk+wLrb1aD2DUisX6pljm7erdu7zOQJUD4+x2Za0MhhEPZhPqWQ9oMxnd5r/1VrAy/UZ1RXH3dpIjgd76Zpt1J X-MS-Exchange-AntiSpam-MessageData: ln1W2PohEIFuuGdBWBtqiOIz9WXxbHf0odANm7d8G5hc/QE8/VoOq4eC0wj19qbPbK/zt0jS/mAQBwbgwvgKgk4pdMGab5p/kVk8X9Wk7SPja71U7crMBWrRVMXZTMSq1gmGk40piMyFP+CAwgri1Upc5va89aP68M8KJwi4af0Hwb/lkfQS4oG9ncoywdV6 X-MS-Exchange-CrossTenant-Network-Message-Id: 54208cfd-b4ef-4d11-c9f0-08d7dda98d70 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2020 23:47:39.3313 (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: LOYPc4hUfMyQtTFehbaf1iJgyDthcxDrQIeXLRQipVh7uBb5wmw0R+kYSh72PF7Y X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW3PR15MB3962 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-10_10:2020-04-09,2020-04-10 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 adultscore=0 clxscore=1015 bulkscore=0 mlxlogscore=999 priorityscore=1501 malwarescore=0 impostorscore=0 phishscore=0 spamscore=0 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004100167 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/10/20 3:53 PM, Andrii Nakryiko wrote: > On Fri, Apr 10, 2020 at 3:43 PM Yonghong Song wrote: >> >> >> >> On 4/9/20 8:00 PM, Alexei Starovoitov wrote: >>> On Wed, Apr 08, 2020 at 04:25:26PM -0700, Yonghong Song wrote: >>>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >>>> index 0f1cbed446c1..b51d56fc77f9 100644 >>>> --- a/include/uapi/linux/bpf.h >>>> +++ b/include/uapi/linux/bpf.h >>>> @@ -354,6 +354,7 @@ enum { >>>> /* Flags for accessing BPF object from syscall side. */ >>>> BPF_F_RDONLY = (1U << 3), >>>> BPF_F_WRONLY = (1U << 4), >>>> + BPF_F_DUMP = (1U << 5), >>> ... >>>> static int bpf_obj_pin(const union bpf_attr *attr) >>>> { >>>> - if (CHECK_ATTR(BPF_OBJ) || attr->file_flags != 0) >>>> + if (CHECK_ATTR(BPF_OBJ) || attr->file_flags & ~BPF_F_DUMP) >>>> return -EINVAL; >>>> >>>> + if (attr->file_flags == BPF_F_DUMP) >>>> + return bpf_dump_create(attr->bpf_fd, >>>> + u64_to_user_ptr(attr->dumper_name)); >>>> + >>>> return bpf_obj_pin_user(attr->bpf_fd, u64_to_user_ptr(attr->pathname)); >>>> } >>> >>> I think kernel can be a bit smarter here. There is no need for user space >>> to pass BPF_F_DUMP flag to kernel just to differentiate the pinning. >>> Can prog attach type be used instead? >> >> Think again. I think a flag is still useful. >> Suppose that we have the following scenario: >> - the current directory /sys/fs/bpf/ >> - user says pin a tracing/dump (target task) prog to "p1" >> >> It is not really clear whether user wants to pin to >> /sys/fs/bpf/p1 >> or user wants to pin to >> /sys/kernel/bpfdump/task/p1 >> >> unless we say that a tracing/dump program cannot pin >> to /sys/fs/bpf which seems unnecessary restriction. >> >> What do you think? > > Instead of special-casing dumper_name, can we require specifying full > path, and then check whether it is in BPF FS vs BPFDUMP FS? If the > latter, additionally check that it is in the right sub-directory > matching its intended target type. We could. I just think specifying full path for bpfdump is not necessary since it is a single user mount... > > But honestly, just doing everything within BPF FS starts to seem > cleaner at this point... bpffs is multi mount, which is not a perfect fit for bpfdump, considering mounting inside namespace, etc, all dumpers are gone.