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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 1722a30a-4a3f-4d74-22ec-08d769590dbc X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Nov 2019 23:19:09.7864 (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: 7bz/ZTmPFWB4ZoSZXCekokQ/n36qSLLaB69fCuik29lMxU7KZXQM5aNJz9OF+CsJMnOmHA0guuFGvIl8FkM7rw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1919 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-14_05:2019-11-14,2019-11-14 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 mlxlogscore=999 adultscore=0 impostorscore=0 bulkscore=0 phishscore=0 spamscore=0 mlxscore=0 suspectscore=0 clxscore=1015 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911140190 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org > On Nov 14, 2019, at 3:01 PM, Alexei Starovoitov wrote: >=20 > On Thu, Nov 14, 2019 at 10:55:37PM +0000, Song Liu wrote: >>=20 >>=20 >>> On Nov 14, 2019, at 10:57 AM, Alexei Starovoitov wrote= : >>>=20 >>> Annotate BPF program context types with program-side type and kernel-si= de type. >>> This type information is used by the verifier. btf_get_prog_ctx_type() = is >>> used in the later patches to verify that BTF type of ctx in BPF program= matches to >>> kernel expected ctx type. For example, the XDP program type is: >>> BPF_PROG_TYPE(BPF_PROG_TYPE_XDP, xdp, struct xdp_md, struct xdp_buff) >>> That means that XDP program should be written as: >>> int xdp_prog(struct xdp_md *ctx) { ... } >>>=20 >>> Signed-off-by: Alexei Starovoitov >>>=20 >>=20 >> [...] >>=20 >>> + /* only compare that prog's ctx type name is the same as >>> + * kernel expects. No need to compare field by field. >>> + * It's ok for bpf prog to do: >>> + * struct __sk_buff {}; >>> + * int socket_filter_bpf_prog(struct __sk_buff *skb) >>> + * { // no fields of skb are ever used } >>> + */ >>> + if (strcmp(ctx_tname, tname)) >>> + return NULL; >>=20 >> Do we need to check size of the two struct? I guess we should not=20 >> allow something like >>=20 >> struct __sk_buff { >> char data[REALLY_BIG_NUM];=20 >> }; >> int socket_filter_bpf_prog(struct __sk_buff *skb) >> { /* access end of skb */ } >=20 > I don't think we should check sizes either. Same comment above applies. T= he > prog's __sk_buff can be different from kernel's view into __sk_buff. Eith= er > bigger or larger doesn't matter. If it's accessed by the prog the verifie= r will > check that all accessed fields are correct. Extra unused fields (like cha= r > data[REALLY_BIG_NUM];) don't affect safety. > When bpf-tracing is attaching to bpf-skb it doesn't use bpf-skb's > __sk_buff with giant fake data[BIG_NUM];. It's using kernel's __sk_buff. > That is what btf_translate_to_vmlinux() in patch 17 is doing. I see. Thanks for the pointer.=20 Song=