| 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-2021-47593: mptcp: clear 'kern' flag from fallback sockets |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mptcp: clear 'kern' flag from fallback sockets |
| |
| The mptcp ULP extension relies on sk->sk_sock_kern being set correctly: |
| It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, "mptcp", 6); from |
| working for plain tcp sockets (any userspace-exposed socket). |
| |
| But in case of fallback, accept() can return a plain tcp sk. |
| In such case, sk is still tagged as 'kernel' and setsockopt will work. |
| |
| This will crash the kernel, The subflow extension has a NULL ctx->conn |
| mptcp socket: |
| |
| BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0 |
| Call Trace: |
| tcp_data_ready+0xf8/0x370 |
| [..] |
| |
| The Linux kernel CVE team has assigned CVE-2021-47593 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.6 with commit cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be and fixed in 5.10.88 with commit 451f1eded7f56e93aaf52eb547ba97742d9c0e97 |
| Issue introduced in 5.6 with commit cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be and fixed in 5.15.11 with commit c26ac0ea3a91c210cf90452e625dc441adf3e549 |
| Issue introduced in 5.6 with commit cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be and fixed in 5.16 with commit d6692b3b97bdc165d150f4c1505751a323a80717 |
| |
| 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-2021-47593 |
| 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/mptcp/protocol.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/451f1eded7f56e93aaf52eb547ba97742d9c0e97 |
| https://git.kernel.org/stable/c/c26ac0ea3a91c210cf90452e625dc441adf3e549 |
| https://git.kernel.org/stable/c/d6692b3b97bdc165d150f4c1505751a323a80717 |
