diff options
author | Michael Kelley <mikelley@microsoft.com> | 2023-03-15 08:34:13 -0700 |
---|---|---|
committer | Wei Liu <wei.liu@kernel.org> | 2023-03-17 10:57:35 +0000 |
commit | f8acb24aaf89fc46cd953229462ea8abe31b395f (patch) | |
tree | 77bb13ecdc7ea24043b60ec4e29e1bf1b54f7906 /arch/x86/kernel/cpu | |
parent | 1eb65c8687316c65140b48fad27133d583178e15 (diff) | |
download | linux-stable-f8acb24aaf89fc46cd953229462ea8abe31b395f.tar.gz linux-stable-f8acb24aaf89fc46cd953229462ea8abe31b395f.tar.bz2 linux-stable-f8acb24aaf89fc46cd953229462ea8abe31b395f.zip |
x86/hyperv: Block root partition functionality in a Confidential VM
Hyper-V should never specify a VM that is a Confidential VM and also
running in the root partition. Nonetheless, explicitly block such a
combination to guard against a compromised Hyper-V maliciously trying to
exploit root partition functionality in a Confidential VM to expose
Confidential VM secrets. No known bug is being fixed, but the attack
surface for Confidential VMs on Hyper-V is reduced.
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1678894453-95392-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu')
-rw-r--r-- | arch/x86/kernel/cpu/mshyperv.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index f36dc2f796c5..f1197366a97d 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -358,12 +358,16 @@ static void __init ms_hyperv_init_platform(void) * To mirror what Windows does we should extract CPU management * features and use the ReservedIdentityBit to detect if Linux is the * root partition. But that requires negotiating CPU management - * interface (a process to be finalized). + * interface (a process to be finalized). For now, use the privilege + * flag as the indicator for running as root. * - * For now, use the privilege flag as the indicator for running as - * root. + * Hyper-V should never specify running as root and as a Confidential + * VM. But to protect against a compromised/malicious Hyper-V trying + * to exploit root behavior to expose Confidential VM memory, ignore + * the root partition setting if also a Confidential VM. */ - if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_CPU_MANAGEMENT) { + if ((ms_hyperv.priv_high & HV_CPU_MANAGEMENT) && + !(ms_hyperv.priv_high & HV_ISOLATION)) { hv_root_partition = true; pr_info("Hyper-V: running as root partition\n"); } |