| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47036: udp: skip L4 aggregation for UDP tunnel packets |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| udp: skip L4 aggregation for UDP tunnel packets |
| |
| If NETIF_F_GRO_FRAGLIST or NETIF_F_GRO_UDP_FWD are enabled, and there |
| are UDP tunnels available in the system, udp_gro_receive() could end-up |
| doing L4 aggregation (either SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST) at |
| the outer UDP tunnel level for packets effectively carrying and UDP |
| tunnel header. |
| |
| That could cause inner protocol corruption. If e.g. the relevant |
| packets carry a vxlan header, different vxlan ids will be ignored/ |
| aggregated to the same GSO packet. Inner headers will be ignored, too, |
| so that e.g. TCP over vxlan push packets will be held in the GRO |
| engine till the next flush, etc. |
| |
| Just skip the SKB_GSO_UDP_L4 and SKB_GSO_FRAGLIST code path if the |
| current packet could land in a UDP tunnel, and let udp_gro_receive() |
| do GRO via udp_sk(sk)->gro_receive. |
| |
| The check implemented in this patch is broader than what is strictly |
| needed, as the existing UDP tunnel could be e.g. configured on top of |
| a different device: we could end-up skipping GRO at-all for some packets. |
| |
| Anyhow, that is a very thin corner case and covering it will add quite |
| a bit of complexity. |
| |
| v1 -> v2: |
| - hopefully clarify the commit message |
| |
| The Linux kernel CVE team has assigned CVE-2021-47036 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.6 with commit 9fd1ff5d2ac7181844735806b0a703c942365291 and fixed in 5.12.4 with commit 450687386cd16d081b58cd7a342acff370a96078 |
| Issue introduced in 5.6 with commit 9fd1ff5d2ac7181844735806b0a703c942365291 and fixed in 5.13 with commit 18f25dc399901426dff61e676ba603ff52c666f7 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47036 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| net/ipv4/udp_offload.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/450687386cd16d081b58cd7a342acff370a96078 |
| https://git.kernel.org/stable/c/18f25dc399901426dff61e676ba603ff52c666f7 |
