Date: Thu, 22 Sep 2016 07:58:47 -0400 (EDT) From: Vladis Dronov <vdronov@...hat.com> To: oss-security@...ts.openwall.com Subject: kernel: ACPI table override is allowed when securelevel is enabled Hello, A vulnerability was found in the RHEL7 kernel. When RHEL7 is booted with UEFI Secure Boot enabled, securelevel is set. The kernel uses the state of securelevel to prevent userspace from inserting untrusted privileged code at runtime. The ACPI tables provided by firmware can be overwritten using the initrd. From the kernel documentation: If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible to override nearly any ACPI table provided by the BIOS with an instrumented, modified one. RHEL7 has CONFIG_ACPI_INITRD_TABLE_OVERRIDE kernel config option enabled, and will load ACPI tables appended to the initrd, even if booted with UEFI Secure Boot enabled and securelevel set. Upstream patch: https://github.com/mjg59/linux/commit/a4a5ed2835e8ea042868b7401dced3f517cafa76 The securelevel patchset was not accepted to an upstream kernel, see http://www.zdnet.com/article/matthew-garrett-is-not-forking-linux/ and https://linux.slashdot.org/story/15/10/06/1553233/matthew-garrett-forks-the-linux-kernel ,it is maintained now by MJG: https://github.com/mjg59/linux . CVE-2016-3699 was assigned to this security flaw internally by the Red Hat. Best regards, Vladis Dronov | Red Hat, Inc. | Product Security Engineer
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Powered by Openwall GNU/*/Linux - Powered by OpenVZ