On Mon, Nov 30, 2020 at 11:17 AM Victor Stewart <v@nametag.social> wrote: > > this being the list of UDP options.. i think we're good here? I'll put > together a new patch. > > https://github.com/torvalds/linux/blob/b65054597872ce3aefbc6a666385eabdf9e288da/include/uapi/linux/udp.h#L30 > > /* UDP socket options */ > #define UDP_CORK 1 /* Never send partially complete segments */ > #define UDP_ENCAP 100 /* Set the socket to accept encapsulated packets */ > #define UDP_NO_CHECK6_TX 101 /* Disable sending checksum for UDP6X */ > #define UDP_NO_CHECK6_RX 102 /* Disable accpeting checksum for UDP6 */ > #define UDP_SEGMENT 103 /* Set GSO segmentation size */ > #define UDP_GRO 104 /* This socket can receive UDP GRO packets */ That is not sufficient proof, because in udp_sendmsg() we also call ip_cmsg_send() in udp_sendmsg(), and ip_cmsg_recv_offset() in udp_recvmsg(). That said, I have audited them and I think they are sane. Jann, what do you think? > On Mon, Nov 30, 2020 at 3:15 PM Soheil Hassas Yeganeh <soheil@xxxxxxxxxx> wrote: > > > > On Mon, Nov 30, 2020 at 10:05 AM Stefan Metzmacher <metze@xxxxxxxxx> wrote: > > > > > > Hi Soheil, > > > > > > > Thank you for CCing us. > > > > > > > > The reason for PROTO_CMSG_DATA_ONLY is explained in the paragraph > > > > above in the commit message. PROTO_CMSG_DATA_ONLY is basically to > > > > allow-list a protocol that is guaranteed not to have the privilege > > > > escalation in https://crbug.com/project-zero/1975. TCP doesn't have > > > > that issue, and I believe UDP doesn't have that issue either (but > > > > please audit and confirm that with +Jann Horn). > > > > > > > > If you couldn't find any non-data CMSGs for UDP, you should just add > > > > PROTO_CMSG_DATA_ONLY to inet dgram sockets instead of introducing > > > > __sys_whitelisted_cmsghdrs as Stefan mentioned. > > > > > > Was there a specific reason why you only added the PROTO_CMSG_DATA_ONLY check > > > in __sys_recvmsg_sock(), but not in __sys_sendmsg_sock()? > > > > We only needed this for recvmsg(MSG_ERRQUEUE) to support transmit > > zerocopy. So, we took a more conservative approach and didn't add it > > for sendmsg(). > > > > I believe it should be fine to add it for TCP sendmsg, because for > > SO_MARK we check the user's capability: > > > > if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) > > return -EPERM; > > > > I believe udp_sendmsg() is sane too and I cannot spot any issue there. > > > > > metze > > > > > > > > >
