| From bippy-1.1.0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@kernel.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2022-49886: x86/tdx: Panic on bad configs that #VE on "private" memory access |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/tdx: Panic on bad configs that #VE on "private" memory access |
| |
| All normal kernel memory is "TDX private memory". This includes |
| everything from kernel stacks to kernel text. Handling |
| exceptions on arbitrary accesses to kernel memory is essentially |
| impossible because they can happen in horribly nasty places like |
| kernel entry/exit. But, TDX hardware can theoretically _deliver_ |
| a virtualization exception (#VE) on any access to private memory. |
| |
| But, it's not as bad as it sounds. TDX can be configured to never |
| deliver these exceptions on private memory with a "TD attribute" |
| called ATTR_SEPT_VE_DISABLE. The guest has no way to *set* this |
| attribute, but it can check it. |
| |
| Ensure ATTR_SEPT_VE_DISABLE is set in early boot. panic() if it |
| is unset. There is no sane way for Linux to run with this |
| attribute clear so a panic() is appropriate. |
| |
| There's small window during boot before the check where kernel |
| has an early #VE handler. But the handler is only for port I/O |
| and will also panic() as soon as it sees any other #VE, such as |
| a one generated by a private memory access. |
| |
| [ dhansen: Rewrite changelog and rebase on new tdx_parse_tdinfo(). |
| Add Kirill's tested-by because I made changes since |
| he wrote this. ] |
| |
| The Linux kernel CVE team has assigned CVE-2022-49886 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.19 with commit 9a22bf6debbf5169f750af53c7f86eb4e3cd6712 and fixed in 6.0.8 with commit 895c168c8f78079f21ad50fead7593ffa352f795 |
| Issue introduced in 5.19 with commit 9a22bf6debbf5169f750af53c7f86eb4e3cd6712 and fixed in 6.1 with commit 373e715e31bf4e0f129befe87613a278fac228d3 |
| |
| 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-2022-49886 |
| 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/coco/tdx/tdx.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/895c168c8f78079f21ad50fead7593ffa352f795 |
| https://git.kernel.org/stable/c/373e715e31bf4e0f129befe87613a278fac228d3 |
