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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-03 09:55:09 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-03 09:55:09 -0800 |
commit | 43c834186c185abc53b41ee985330501ccfc4f7b (patch) | |
tree | added7ba55d438d8102b9c1646013923ea2d2ea6 /arch/x86/kernel/sev-es-shared.c | |
parent | f4c79144edd8a49ffca8fa737a31d606be742a34 (diff) | |
parent | 2411cd82112397bfb9d8f0f19cd46c3d71e0ce67 (diff) | |
download | linux-43c834186c185abc53b41ee985330501ccfc4f7b.tar.bz2 |
Merge tag 'x86_seves_for_v5.10_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV-ES fixes from Borislav Petkov:
"A couple of changes to the SEV-ES code to perform more stringent
hypervisor checks before enabling encryption (Joerg Roedel)"
* tag 'x86_seves_for_v5.10_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/sev-es: Do not support MMIO to/from encrypted memory
x86/head/64: Check SEV encryption before switching to kernel page-table
x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path
x86/boot/compressed/64: Sanity-check CPUID results in the early #VC handler
x86/boot/compressed/64: Introduce sev_status
Diffstat (limited to 'arch/x86/kernel/sev-es-shared.c')
-rw-r--r-- | arch/x86/kernel/sev-es-shared.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c index 5f83ccaab877..7d04b356d44d 100644 --- a/arch/x86/kernel/sev-es-shared.c +++ b/arch/x86/kernel/sev-es-shared.c @@ -178,6 +178,32 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) goto fail; regs->dx = val >> 32; + /* + * This is a VC handler and the #VC is only raised when SEV-ES is + * active, which means SEV must be active too. Do sanity checks on the + * CPUID results to make sure the hypervisor does not trick the kernel + * into the no-sev path. This could map sensitive data unencrypted and + * make it accessible to the hypervisor. + * + * In particular, check for: + * - Hypervisor CPUID bit + * - Availability of CPUID leaf 0x8000001f + * - SEV CPUID bit. + * + * The hypervisor might still report the wrong C-bit position, but this + * can't be checked here. + */ + + if ((fn == 1 && !(regs->cx & BIT(31)))) + /* Hypervisor bit */ + goto fail; + else if (fn == 0x80000000 && (regs->ax < 0x8000001f)) + /* SEV leaf check */ + goto fail; + else if ((fn == 0x8000001f && !(regs->ax & BIT(1)))) + /* SEV bit */ + goto fail; + /* Skip over the CPUID two-byte opcode */ regs->ip += 2; |