OvmfPkg/AmdSev/SecretDxe: Allocate secret location as EfiACPIReclaimMemory

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4186

Commit 079a58276b98 ("OvmfPkg/AmdSev/SecretPei: Mark SEV launch secret
area as reserved") marked the launch secret area itself (1 page) as
reserved so the guest OS can use it during the lifetime of the OS.
However, the address and size of the secret area held in the
CONFIDENTIAL_COMPUTING_SECRET_LOCATION struct are declared as STATIC in
OVMF (in AmdSev/SecretDxe); therefore there's no guarantee that it will
not be written over by OS data.

Fix this by allocating the memory for the
CONFIDENTIAL_COMPUTING_SECRET_LOCATION struct with the
EfiACPIReclaimMemory memory type to ensure the guest OS will not reuse
this memory.

Fixes: 079a58276b98 ("OvmfPkg/AmdSev/SecretPei: Mark SEV launch secret ...")
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 16 insertions, 6 deletions

diff --git a/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c b/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
index 3d84b25450..c3258570e9 100644
--- a/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
+++ b/OvmfPkg/AmdSev/SecretDxe/SecretDxe.c
@@ -8,11 +8,6 @@
 #include <Library/UefiBootServicesTableLib.h>

 #include <Guid/ConfidentialComputingSecret.h>

 

-STATIC CONFIDENTIAL_COMPUTING_SECRET_LOCATION  mSecretDxeTable = {

-  FixedPcdGet32 (PcdSevLaunchSecretBase),

-  FixedPcdGet32 (PcdSevLaunchSecretSize),

-};

-

 EFI_STATUS

 EFIAPI

 InitializeSecretDxe (

@@ -20,8 +15,23 @@ InitializeSecretDxe (
   IN EFI_SYSTEM_TABLE  *SystemTable

   )

 {

+  EFI_STATUS                              Status;

+  CONFIDENTIAL_COMPUTING_SECRET_LOCATION  *SecretDxeTable;

+

+  Status = gBS->AllocatePool (

+                  EfiACPIReclaimMemory,

+                  sizeof (CONFIDENTIAL_COMPUTING_SECRET_LOCATION),

+                  (VOID **)&SecretDxeTable

+                  );

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  SecretDxeTable->Base = FixedPcdGet32 (PcdSevLaunchSecretBase);

+  SecretDxeTable->Size = FixedPcdGet32 (PcdSevLaunchSecretSize);

+

   return gBS->InstallConfigurationTable (

                 &gConfidentialComputingSecretGuid,

-                &mSecretDxeTable

+                SecretDxeTable

                 );

 }