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Thu, 14 May 2020 14:59:02 +0000 Subject: Re: [PATCH bpf v2 1/2] bpf: enforce returning 0 for fentry/fexit progs To: Andrii Nakryiko CC: bpf , Alexei Starovoitov , Daniel Borkmann , Kernel Team References: <20200514053205.1298315-1-yhs@fb.com> <20200514053206.1298415-1-yhs@fb.com> From: Yonghong Song Message-ID: Date: Thu, 14 May 2020 07:58:59 -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: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY5PR13CA0005.namprd13.prod.outlook.com (2603:10b6:a03:180::18) 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 (2620:10d:c090:400::5:3bff) by BY5PR13CA0005.namprd13.prod.outlook.com (2603:10b6:a03:180::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3021.11 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: qPiNRBqc2mIOnsGLHqdSnYqmxuwzEoBVmPRkTpzCxdvg2aTf2YYbkh0u8XwwkgRw7Qqfh5YqIzAkALgq/YOVQndN7w8EUZVJfDTru/QX8OF+dVDhEyAKKhoTY6aCuVQbEjFj1OOEO1DtMX/IKVGd3ZfiQLx03I9h24tr7NRaZlgXxDkpSQXa14ftb747fiFhprZE+OURg1nVd1MXp/SLilkap/cGVITK6rZWSQyPAcwGHFer9SK0Q1JyKJ+s8eN0MCWN7U44+9trjZN8CWGhr9pw6bSwcDVID1dld938vwSHu8Uo9cAD6HZvViRVYbYPOEpJ6RnXx38dzGHQ7E/hkrIOuITtEg5uXrvWSMrkfRNElp8NDZ6S6MH2a+iqtsaBFkiQOxdbPE9dkF9SXjC+xEwvf4xkeQNDhSclhylUKZ4xcbVUoD7qGKqzzXIb5CzbzJWhsZImzpoO6o6WVv+HB4RTvhu9SWTY2bNcAxTr+R7FNyXwgwOuk9qS5C7xvVk6O9KX1BudBuXB7JbJ2OOqSw== X-MS-Exchange-CrossTenant-Network-Message-Id: 77df4bbf-e20b-43db-a0fe-08d7f81756c9 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 May 2020 14:59:02.2513 (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: dDukfqxNUlb7oNg+tzwVUJGhE0y+gm/6VUkQnJi95Q2argxj34K3YpqYSo4RpXwj X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2629 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-14_05:2020-05-14,2020-05-14 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 spamscore=0 priorityscore=1501 suspectscore=0 cotscore=-2147483648 mlxscore=0 malwarescore=0 adultscore=0 bulkscore=0 clxscore=1015 mlxlogscore=999 impostorscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005140132 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 5/13/20 11:14 PM, Andrii Nakryiko wrote: > On Wed, May 13, 2020 at 10:32 PM Yonghong Song wrote: >> >> Currently, tracing/fentry and tracing/fexit prog >> return values are not enforced. In trampoline codes, >> the fentry/fexit prog return values are ignored. >> Let us enforce it to be 0 to avoid confusion and >> allows potential future extension. >> >> This patch also explicitly added return value >> checking for tracing/raw_tp, tracing/fmod_ret, >> and freplace programs such that these program >> return values can be anything. The purpose are >> two folds: >> 1. to make it explicit about return value expectations >> for these programs in verifier. >> 2. for tracing prog_type, if a future attach type >> is added, the default is -ENOTSUPP which will >> enforce to specify return value ranges explicitly. >> >> Fixes: fec56f5890d9 ("bpf: Introduce BPF trampoline") >> Signed-off-by: Yonghong Song >> --- > > Looks good, except a nit below. > > Acked-by: Andrii Nakryiko > > [...] > >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> index fa1d8245b925..2d80cce0a28a 100644 >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c >> @@ -7059,6 +7059,24 @@ static int check_return_code(struct bpf_verifier_env *env) >> return 0; >> range = tnum_const(0); >> break; >> + case BPF_PROG_TYPE_TRACING: >> + switch ((env->prog->expected_attach_type)) { > > nit: extra pair of ()? Sorry about this. Not sure whether it is worthwhile to send another revision. Please let me know if another revision is needed. > > >> + case BPF_TRACE_FENTRY: >> + case BPF_TRACE_FEXIT: >> + range = tnum_const(0); >> + break; >> + case BPF_TRACE_RAW_TP: >> + case BPF_MODIFY_RETURN: >> + return 0; >> + default: >> + return -ENOTSUPP; >> + } >> + >> + break; >> + case BPF_PROG_TYPE_EXT: >> + /* freplace program can return anything as its return value >> + * depends on the to-be-replaced kernel func or bpf program. >> + */ >> default: >> return 0; >> } >> -- >> 2.24.1 >>