Date: Wed, 07 Dec 2022 15:24:25 +0000 From: Xen.org security team <security@....org> To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org, xen-users@...ts.xen.org, oss-security@...ts.openwall.com CC: Xen.org security team <security-team-members@....org> Subject: Xen Security Advisory 423 v2 (CVE-2022-3643) - Guests can trigger NIC interface reset/abort/crash via netback -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2022-3643 / XSA-423 version 2 Guests can trigger NIC interface reset/abort/crash via netback UPDATES IN VERSION 2 ==================== Patch updated. ISSUE DESCRIPTION ================= It is possible for a guest to trigger a NIC interface reset/abort/crash in a Linux based network backend by sending certain kinds of packets. It appears to be an (unwritten?) assumption in the rest of the Linux network stack that packet protocol headers are all contained within the linear section of the SKB and some NICs behave badly if this is not the case. This has been reported to occur with Cisco (enic) and Broadcom NetXtrem II BCM5780 (bnx2x) though it may be an issue with other NICs/drivers as well. In case the frontend is sending requests with split headers, netback will forward those violating above mentioned assumption to the networking core, resulting in said misbehavior. IMPACT ====== An unprivileged guest can cause network Denial of Service (DoS) of the host by sending network packets to the backend causing the related physical NIC to reset, abort, or crash. Data corruption or privilege escalation seem unlikely but have not been ruled out. VULNERABLE SYSTEMS ================== All systems using a Linux based network backend with kernel 3.19 and newer are vulnerable. Systems using other network backends are not known to be vulnerable. Systems using Cisco (enic driver) and Broadcom NetXtrem II BCM5780 (bnx2x driver) NICs for guest network access are known to be vulnerable. Systems using other NICs for guest network access cannot be ruled out to be vulnerable. MITIGATION ========== Using another PV network backend (e.g. the qemu based "qnic" backend) will mitigate the problem. Using a dedicated network driver domain per guest will mitigate the problem. NOTE REGARDING LACK OF EMBARGO ============================== This issue was discussed in public already. RESOLUTION ========== Applying the attached patch resolves this issue. xsa423-linux.patch Linux 4.14 - 6.1-rc $ sha256sum xsa423* e26ab5aa05cad09a26ebf12ef6e6197145937d5ae2ada6f6bb824af81ddf3916 xsa423-linux.patch $ -----BEGIN PGP SIGNATURE----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAmOQr+IMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZP1MIAL6GhGU7LQrsi1w9DC4NbnbYMJ7uwEz0k6w0++n6 IEB3+5k0Di20TdWJC7fhdi4GZMEfqfs6vJ5nN4oy3m1hsy2fU3CtEcrknba91NL/ 7O9N+z6tN4Sy163Mhe/LHaaYLt/R1L98HiQQnGNaTeybJDVhrEByucKhCum7Tasr AKcMK7M2/nevciOsbwnuAtoz9o+WQJBkVevMfjIL5NMg1wHevDM6BEzZ9bhQakY+ YIf2rSVNuEzQ84dhwa+vzvjv9Ywvwyo1iNNnavUiEtqn0ZeZkuqcL/o3g6v/WjKC Rm4+Kc3RGSlw8i5/MB46Zq91kf9H3ccW2hyzred1byAy07g= =x7us -----END PGP SIGNATURE----- Download attachment "xsa423-linux.patch" of type "application/octet-stream" (12868 bytes)
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