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Wed, 19 Aug 2020 01:42:27 +0000 Subject: Re: [PATCH bpf-next 4/7] libbpf: sanitize BPF program code for bpf_probe_read_{kernel,user}[_str] To: Andrii Nakryiko , , , , CC: , References: <20200818213356.2629020-1-andriin@fb.com> <20200818213356.2629020-5-andriin@fb.com> From: Yonghong Song Message-ID: Date: Tue, 18 Aug 2020 18:42:22 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 In-Reply-To: <20200818213356.2629020-5-andriin@fb.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MN2PR16CA0034.namprd16.prod.outlook.com (2603:10b6:208:134::47) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c0a8:11e8::10d3] (2620:10d:c091:480::1:a06c) by MN2PR16CA0034.namprd16.prod.outlook.com (2603:10b6:208:134::47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3305.24 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 50cc8eab-d12a-47b0-56c8-08d843e120e8 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Aug 2020 01:42:27.3863 (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: VQZ9L4n3FKAvYJLyAM+kcZ379WiHSrtL7tp30vb9ChOOeA42NOc21Cb4EGg178Nr X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR15MB3569 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-18_16:2020-08-18,2020-08-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 impostorscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 malwarescore=0 lowpriorityscore=0 suspectscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008190014 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 8/18/20 2:33 PM, Andrii Nakryiko wrote: > Add BPF program code sanitization pass, replacing calls to BPF > bpf_probe_read_{kernel,user}[_str]() helpers with bpf_probe_read[_str](), if > libbpf detects that kernel doesn't support new variants. I know this has been merged. The whole patch set looks good to me. A few nit or questions below. > > Signed-off-by: Andrii Nakryiko > --- > tools/lib/bpf/libbpf.c | 80 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 80 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index ab0c3a409eea..bdc08f89a5c0 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -180,6 +180,8 @@ enum kern_feature_id { > FEAT_ARRAY_MMAP, > /* kernel support for expected_attach_type in BPF_PROG_LOAD */ > FEAT_EXP_ATTACH_TYPE, > + /* bpf_probe_read_{kernel,user}[_str] helpers */ > + FEAT_PROBE_READ_KERN, > __FEAT_CNT, > }; > > @@ -3591,6 +3593,27 @@ static int probe_kern_exp_attach_type(void) > return probe_fd(bpf_load_program_xattr(&attr, NULL, 0)); > } > [...] > > +static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id) > +{ > + __u8 class = BPF_CLASS(insn->code); > + > + if ((class == BPF_JMP || class == BPF_JMP32) && Do we support BPF_JMP32 + BPF_CALL ... as a helper call? I am not aware of this. > + BPF_OP(insn->code) == BPF_CALL && > + BPF_SRC(insn->code) == BPF_K && > + insn->src_reg == 0 && insn->dst_reg == 0) { > + if (func_id) > + *func_id = insn->imm; looks like func_id is always non-NULL. Unless this is to support future usage where func_id may be NULL, the above condition probably not needed. > + return true; > + } > + return false; > +} > + [...]