From: "tip-bot2 for Joerg Roedel" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Joerg Roedel <jroedel@suse.de>, Borislav Petkov <bp@suse.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/seves] x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path
Date: Thu, 18 Mar 2021 22:10:17 -0000 [thread overview]
Message-ID: <161610541745.398.5004496051877898127.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210312123824.306-7-joro@8bytes.org>
The following commit has been merged into the x86/seves branch of tip:
Commit-ID: e927e62d8e370ebfc0d702fec22bc752249ebcef
Gitweb: https://git.kernel.org/tip/e927e62d8e370ebfc0d702fec22bc752249ebcef
Author: Joerg Roedel <jroedel@suse.de>
AuthorDate: Fri, 12 Mar 2021 13:38:22 +01:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Thu, 18 Mar 2021 23:04:12 +01:00
x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path
The 32-bit #VC handler has no GHCB and can only handle CPUID exit codes.
It is needed by the early boot code to handle #VC exceptions raised in
verify_cpu() and to get the position of the C-bit.
But the CPUID information comes from the hypervisor which is untrusted
and might return results which trick the guest into the no-SEV boot path
with no C-bit set in the page-tables. All data written to memory would
then be unencrypted and could leak sensitive data to the hypervisor.
Add sanity checks to the 32-bit boot #VC handler to make sure the
hypervisor does not pretend that SEV is not enabled.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210312123824.306-7-joro@8bytes.org
---
arch/x86/boot/compressed/mem_encrypt.S | 28 +++++++++++++++++++++++++-
1 file changed, 28 insertions(+)
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index ebc4a29..c1e81a8 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -139,6 +139,26 @@ SYM_CODE_START(startup32_vc_handler)
jnz .Lfail
movl %edx, 0(%esp) # Store result
+ /*
+ * Sanity check CPUID results from the Hypervisor. See comment in
+ * do_vc_no_ghcb() for more details on why this is necessary.
+ */
+
+ /* Fail if SEV leaf not available in CPUID[0x80000000].EAX */
+ cmpl $0x80000000, %ebx
+ jne .Lcheck_sev
+ cmpl $0x8000001f, 12(%esp)
+ jb .Lfail
+ jmp .Ldone
+
+.Lcheck_sev:
+ /* Fail if SEV bit not set in CPUID[0x8000001f].EAX[1] */
+ cmpl $0x8000001f, %ebx
+ jne .Ldone
+ btl $1, 12(%esp)
+ jnc .Lfail
+
+.Ldone:
popl %edx
popl %ecx
popl %ebx
@@ -152,6 +172,14 @@ SYM_CODE_START(startup32_vc_handler)
iret
.Lfail:
+ /* Send terminate request to Hypervisor */
+ movl $0x100, %eax
+ xorl %edx, %edx
+ movl $MSR_AMD64_SEV_ES_GHCB, %ecx
+ wrmsr
+ rep; vmmcall
+
+ /* If request fails, go to hlt loop */
hlt
jmp .Lfail
SYM_CODE_END(startup32_vc_handler)
next prev parent reply other threads:[~2021-03-18 22:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 12:38 [PATCH v3 0/8] x86/seves: Support 32-bit boot path and other updates Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 1/8] x86/boot/compressed/64: Cleanup exception handling before booting kernel Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 2/8] x86/sev: Do not require Hypervisor CPUID bit for SEV guests Joerg Roedel
2021-03-17 15:04 ` Tom Lendacky
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 3/8] x86/boot/compressed/64: Reload CS in startup_32 Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 4/8] x86/boot/compressed/64: Setup IDT in startup_32 boot path Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 5/8] x86/boot/compressed/64: Add 32-bit boot #VC handler Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-18 22:10 ` tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 6/8] x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-18 22:10 ` tip-bot2 for Joerg Roedel [this message]
2021-03-12 12:38 ` [PATCH v3 7/8] x86/boot/compressed/64: Check SEV encryption in " Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] x86/boot/compressed/64: Check SEV encryption in the " tip-bot2 for Joerg Roedel
2021-03-18 22:10 ` tip-bot2 for Joerg Roedel
2021-03-12 12:38 ` [PATCH v3 8/8] x86/sev-es: Replace open-coded hlt-loops with sev_es_terminate() Joerg Roedel
2021-03-18 19:34 ` [tip: x86/seves] " tip-bot2 for Joerg Roedel
2021-03-18 22:10 ` tip-bot2 for Joerg Roedel
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