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Wed, 19 Aug 2020 20:13:29 +0000 Subject: Re: [PATCH bpf-next 4/6] bpf: override the meaning of ARG_PTR_TO_MAP_VALUE for sockmap and sockhash To: Lorenz Bauer , , , Alexei Starovoitov , Daniel Borkmann CC: , , , References: <20200819092436.58232-1-lmb@cloudflare.com> <20200819092436.58232-5-lmb@cloudflare.com> From: Yonghong Song Message-ID: <5d64158b-35ed-d28d-9857-6ee725d287f2@fb.com> Date: Wed, 19 Aug 2020 13:13:23 -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: <20200819092436.58232-5-lmb@cloudflare.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MN2PR18CA0002.namprd18.prod.outlook.com (2603:10b6:208:23c::7) 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:d29f) by MN2PR18CA0002.namprd18.prod.outlook.com (2603:10b6:208:23c::7) 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: 975ee0cd-1c71-456a-f122-08d8447c5697 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Aug 2020 20:13:29.5065 (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: IBT3wjijnVvM95ziKdyCvSVV+u2AUozknx5fnvHdMc9FmNbdNiFR/JM/ZDtE1/Qk X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2645 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-19_13:2020-08-19,2020-08-19 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 spamscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 mlxscore=0 adultscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008190164 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/19/20 2:24 AM, Lorenz Bauer wrote: > The verifier assumes that map values are simple blobs of memory, and > therefore treats ARG_PTR_TO_MAP_VALUE, etc. as such. However, there are > map types where this isn't true. For example, sockmap and sockhash store > sockets. In general this isn't a big problem: we can just > write helpers that explicitly requests PTR_TO_SOCKET instead of > ARG_PTR_TO_MAP_VALUE. > > The one exception are the standard map helpers like map_update_elem, > map_lookup_elem, etc. Here it would be nice we could overload the > function prototype for different kinds of maps. Unfortunately, this > isn't entirely straight forward: > We only know the type of the map once we have resolved meta->map_ptr > in check_func_arg. This means we can't swap out the prototype > in check_helper_call until we're half way through the function. > > Instead, modify check_func_arg to treat ARG_PTR_TO_MAP_VALUE* to > mean "the native type for the map" instead of "pointer to memory" > for sockmap and sockhash. This means we don't have to modify the > function prototype at all > > Signed-off-by: Lorenz Bauer > --- > kernel/bpf/verifier.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index b6ccfce3bf4c..47f9b94bb9d4 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -3872,6 +3872,38 @@ static int int_ptr_type_to_size(enum bpf_arg_type type) > return -EINVAL; > } > > +static int override_map_arg_type(struct bpf_verifier_env *env, > + const struct bpf_call_arg_meta *meta, > + enum bpf_arg_type *arg_type) > +{ > + if (!meta->map_ptr) { > + /* kernel subsystem misconfigured verifier */ > + verbose(env, "invalid map_ptr to access map->type\n"); > + return -EACCES; > + } > + > + switch (meta->map_ptr->map_type) { > + case BPF_MAP_TYPE_SOCKMAP: > + case BPF_MAP_TYPE_SOCKHASH: > + switch (*arg_type) { > + case ARG_PTR_TO_MAP_VALUE: > + *arg_type = ARG_PTR_TO_SOCKET; > + break; > + case ARG_PTR_TO_MAP_VALUE_OR_NULL: > + *arg_type = ARG_PTR_TO_SOCKET_OR_NULL; > + break; > + default: > + verbose(env, "invalid arg_type for sockmap/sockhash\n"); > + return -EINVAL; > + } > + break; > + > + default: > + break; > + } > + return 0; > +} > + > static int check_func_arg(struct bpf_verifier_env *env, u32 arg, > struct bpf_call_arg_meta *meta, > const struct bpf_func_proto *fn) > @@ -3904,6 +3936,14 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, > return -EACCES; > } > > + if (arg_type == ARG_PTR_TO_MAP_VALUE || > + arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE || > + arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) { We probably do not need ARG_PTR_TO_UNINIT_MAP_VALUE here. Do we need ARG_PTR_TO_MAP_VALUE_OR_NULL? bpf_map_update_elem arg type is ARG_PTR_TO_MAP_VALUE. > + err = override_map_arg_type(env, meta, &arg_type); > + if (err) > + return err; > + } > + > if (arg_type == ARG_PTR_TO_MAP_KEY || > arg_type == ARG_PTR_TO_MAP_VALUE || > arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE || >