| 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-2023-52568: x86/sgx: Resolves SECS reclaim vs. page fault for EAUG race |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/sgx: Resolves SECS reclaim vs. page fault for EAUG race |
| |
| The SGX EPC reclaimer (ksgxd) may reclaim the SECS EPC page for an |
| enclave and set secs.epc_page to NULL. The SECS page is used for EAUG |
| and ELDU in the SGX page fault handler. However, the NULL check for |
| secs.epc_page is only done for ELDU, not EAUG before being used. |
| |
| Fix this by doing the same NULL check and reloading of the SECS page as |
| needed for both EAUG and ELDU. |
| |
| The SECS page holds global enclave metadata. It can only be reclaimed |
| when there are no other enclave pages remaining. At that point, |
| virtually nothing can be done with the enclave until the SECS page is |
| paged back in. |
| |
| An enclave can not run nor generate page faults without a resident SECS |
| page. But it is still possible for a #PF for a non-SECS page to race |
| with paging out the SECS page: when the last resident non-SECS page A |
| triggers a #PF in a non-resident page B, and then page A and the SECS |
| both are paged out before the #PF on B is handled. |
| |
| Hitting this bug requires that race triggered with a #PF for EAUG. |
| Following is a trace when it happens. |
| |
| BUG: kernel NULL pointer dereference, address: 0000000000000000 |
| RIP: 0010:sgx_encl_eaug_page+0xc7/0x210 |
| Call Trace: |
| ? __kmem_cache_alloc_node+0x16a/0x440 |
| ? xa_load+0x6e/0xa0 |
| sgx_vma_fault+0x119/0x230 |
| __do_fault+0x36/0x140 |
| do_fault+0x12f/0x400 |
| __handle_mm_fault+0x728/0x1110 |
| handle_mm_fault+0x105/0x310 |
| do_user_addr_fault+0x1ee/0x750 |
| ? __this_cpu_preempt_check+0x13/0x20 |
| exc_page_fault+0x76/0x180 |
| asm_exc_page_fault+0x27/0x30 |
| |
| The Linux kernel CVE team has assigned CVE-2023-52568 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.0 with commit 5a90d2c3f5ef87717e54572af8426aba6fdbdaa6 and fixed in 6.1.56 with commit 811ba2ef0cb6402672e64ba1419d6ef95aa3405d |
| Issue introduced in 6.0 with commit 5a90d2c3f5ef87717e54572af8426aba6fdbdaa6 and fixed in 6.5.6 with commit 1348f7f15d7c7798456856bee74a4235c2da994e |
| Issue introduced in 6.0 with commit 5a90d2c3f5ef87717e54572af8426aba6fdbdaa6 and fixed in 6.6 with commit c6c2adcba50c2622ed25ba5d5e7f05f584711358 |
| |
| 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-2023-52568 |
| 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: |
| arch/x86/kernel/cpu/sgx/encl.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/811ba2ef0cb6402672e64ba1419d6ef95aa3405d |
| https://git.kernel.org/stable/c/1348f7f15d7c7798456856bee74a4235c2da994e |
| https://git.kernel.org/stable/c/c6c2adcba50c2622ed25ba5d5e7f05f584711358 |
