Date: Mon, 5 Aug 2019 22:04:16 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r350619 - in stable: 11/usr.sbin/bhyve 12/usr.sbin/bhyve Message-ID: <201908052204.x75M4Gap054896@repo.freebsd.org>
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Author: jhb Date: Mon Aug 5 22:04:16 2019 New Revision: 350619 URL: https://svnweb.freebsd.org/changeset/base/350619 Log: MFC 350618: Validate guest-supplied length of headers for TSO transmit requests. When transmitting a large TCP packet, the final transmit descriptor includes the length of the protocol headers to be duplicated on each segment. The device model was trusting the guest-supplied value without validating it. A value of zero would result in the guest being able to indirect a garbage pointer on the stack to overwrite arbitrary memory in the bhyve process. A value that was non-zero but too small for the requested parameters resulted in the device model reading and writing values beyond the end of the on-stack buffer used to hold the template header. To fix, validate the supplied length and drop requests to transmit packets that would overflow the header buffer. While here, initialize the header pointer to NULL as a preventive measure so that any access to an unallocated template header crashes they hypervisor deterministically. While here, only read the TCP sequence number if the packet being split is a TCP packet. The e1000 logic supports a segmentation of UDP frames, and while UDP segmentation requires this part of the header to be valid (so there is no buffer overflow), only reading the field when needed is cleaner. admbugs: 918 Reported by: Reno Robert <renorobert@gmail.com> Approved by: so Security: CVE-2019-5609 Modified: stable/11/usr.sbin/bhyve/pci_e82545.c Directory Properties: stable/11/ (props changed) Changes in other areas also in this revision: Modified: stable/12/usr.sbin/bhyve/pci_e82545.c Directory Properties: stable/12/ (props changed) Modified: stable/11/usr.sbin/bhyve/pci_e82545.c ============================================================================== --- stable/11/usr.sbin/bhyve/pci_e82545.c Mon Aug 5 21:39:55 2019 (r350618) +++ stable/11/usr.sbin/bhyve/pci_e82545.c Mon Aug 5 22:04:16 2019 (r350619) @@ -1079,8 +1079,9 @@ e82545_transmit(struct e82545_softc *sc, uint16_t head struct ck_info ckinfo[2]; struct iovec *iov; union e1000_tx_udesc *dsc; - int desc, dtype, len, ntype, iovcnt, tlen, hdrlen, vlen, tcp, tso; + int desc, dtype, len, ntype, iovcnt, tlen, tcp, tso; int mss, paylen, seg, tiovcnt, left, now, nleft, nnow, pv, pvoff; + unsigned hdrlen, vlen; uint32_t tcpsum, tcpseq; uint16_t ipcs, tcpcs, ipid, ohead; @@ -1224,6 +1225,68 @@ e82545_transmit(struct e82545_softc *sc, uint16_t head } else { /* In case of TSO header length provided by software. */ hdrlen = sc->esc_txctx.tcp_seg_setup.fields.hdr_len; + + /* + * Cap the header length at 240 based on 7.2.4.5 of + * the Intel 82576EB (Rev 2.63) datasheet. + */ + if (hdrlen > 240) { + WPRINTF("TSO hdrlen too large: %d\r\n", hdrlen); + goto done; + } + + /* + * If VLAN insertion is requested, ensure the header + * at least holds the amount of data copied during + * VLAN insertion below. + * + * XXX: Realistic packets will include a full Ethernet + * header before the IP header at ckinfo[0].ck_start, + * but this check is sufficient to prevent + * out-of-bounds access below. + */ + if (vlen != 0 && hdrlen < ETHER_ADDR_LEN*2) { + WPRINTF("TSO hdrlen too small for vlan insertion " + "(%d vs %d) -- dropped\r\n", hdrlen, + ETHER_ADDR_LEN*2); + goto done; + } + + /* + * Ensure that the header length covers the used fields + * in the IP and TCP headers as well as the IP and TCP + * checksums. The following fields are accessed below: + * + * Header | Field | Offset | Length + * -------+-------+--------+------- + * IPv4 | len | 2 | 2 + * IPv4 | ID | 4 | 2 + * IPv6 | len | 4 | 2 + * TCP | seq # | 4 | 4 + * TCP | flags | 13 | 1 + * UDP | len | 4 | 4 + */ + if (hdrlen < ckinfo[0].ck_start + 6 || + hdrlen < ckinfo[0].ck_off + 2) { + WPRINTF("TSO hdrlen too small for IP fields (%d) " + "-- dropped\r\n", hdrlen); + goto done; + } + if (sc->esc_txctx.cmd_and_length & E1000_TXD_CMD_TCP) { + if (hdrlen < ckinfo[1].ck_start + 14 || + (ckinfo[1].ck_valid && + hdrlen < ckinfo[1].ck_off + 2)) { + WPRINTF("TSO hdrlen too small for TCP fields " + "(%d) -- dropped\r\n", hdrlen); + goto done; + } + } else { + if (hdrlen < ckinfo[1].ck_start + 8) { + WPRINTF("TSO hdrlen too small for UDP fields " + "(%d) -- dropped\r\n", hdrlen); + goto done; + } + } } /* Allocate, fill and prepend writable header vector. */ @@ -1245,7 +1308,8 @@ e82545_transmit(struct e82545_softc *sc, uint16_t head iovcnt++; iov->iov_base = hdr; iov->iov_len = hdrlen; - } + } else + hdr = NULL; /* Insert VLAN tag. */ if (vlen != 0) { @@ -1287,7 +1351,9 @@ e82545_transmit(struct e82545_softc *sc, uint16_t head DPRINTF("tx %s segmentation offload %d+%d/%d bytes %d iovs\r\n", tcp ? "TCP" : "UDP", hdrlen, paylen, mss, iovcnt); ipid = ntohs(*(uint16_t *)&hdr[ckinfo[0].ck_start + 4]); - tcpseq = ntohl(*(uint32_t *)&hdr[ckinfo[1].ck_start + 4]); + tcpseq = 0; + if (tcp) + tcpseq = ntohl(*(uint32_t *)&hdr[ckinfo[1].ck_start + 4]); ipcs = *(uint16_t *)&hdr[ckinfo[0].ck_off]; tcpcs = 0; if (ckinfo[1].ck_valid) /* Save partial pseudo-header checksum. */
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