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Tue, 12 May 2020 15:41:21 +0000 Subject: Re: [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program To: Alexei Starovoitov CC: Andrii Nakryiko , , Martin KaFai Lau , , Alexei Starovoitov , Daniel Borkmann , References: <20200509175859.2474608-1-yhs@fb.com> <20200509175900.2474947-1-yhs@fb.com> <20200510004139.tjlll6wqq7zevb73@ast-mbp> From: Yonghong Song Message-ID: Date: Tue, 12 May 2020 08:41:19 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 In-Reply-To: <20200510004139.tjlll6wqq7zevb73@ast-mbp> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR01CA0037.prod.exchangelabs.com (2603:10b6:a03:94::14) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from macbook-pro-52.local.dhcp.thefacebook.com (2620:10d:c090:400::5:d0f0) by BYAPR01CA0037.prod.exchangelabs.com (2603:10b6:a03:94::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3000.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: d550903b-ce91-47a9-a4ae-08d7f68aeb22 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 May 2020 15:41:21.0258 (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: Tp3LWQplq4bQjjZd44LqJebXsm+vTwPhVvAkhAvhNjVjT78UumZ8uzjIVfWbo54a X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2968 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-12_04:2020-05-11,2020-05-12 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 mlxlogscore=999 clxscore=1015 bulkscore=0 phishscore=0 impostorscore=0 spamscore=0 mlxscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005120118 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 5/9/20 5:41 PM, Alexei Starovoitov wrote: > On Sat, May 09, 2020 at 10:59:00AM -0700, Yonghong Song wrote: >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index 70ad009577f8..d725ff7d11db 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -7101,6 +7101,10 @@ static int check_return_code(struct bpf_verifier_env *env) >> return 0; >> range = tnum_const(0); >> break; >> + case BPF_PROG_TYPE_TRACING: >> + if (env->prog->expected_attach_type != BPF_TRACE_ITER) >> + return 0; >> + break; > > Not related to this set, but I just noticed that I managed to forget to > add this check for fentry/fexit/freplace. > While it's not too late let's enforce return 0 for them ? > Could you follow up with a patch for bpf tree? Just want to double check. In selftests, we have SEC("fentry/__set_task_comm") int BPF_PROG(prog4, struct task_struct *tsk, const char *buf, bool exec) { return !tsk; } SEC("fexit/__set_task_comm") int BPF_PROG(prog5, struct task_struct *tsk, const char *buf, bool exec) { return !tsk; } fentry/fexit may returrn 1. What is the intention here? Does this mean we should allow [0, 1] instead of [0, 0]? For freplace, we have __u64 test_get_skb_len = 0; SEC("freplace/get_skb_len") int new_get_skb_len(struct __sk_buff *skb) { int len = skb->len; if (len != 74) return 0; test_get_skb_len = 1; return 74; /* original get_skb_len() returns skb->len */ } That means freplace may return arbitrary values depending on what to replace?