tpm: return a TPM_RC_COMMAND_CODE response if command is not implemented

[ Upstream commit 095531f891e627e408606f2da4008d3d53e6748a ]

According to the TPM Library Specification, a TPM device must do a command
header validation before processing and return a TPM_RC_COMMAND_CODE code
if the command is not implemented.

So user-space will expect to handle that response as an error. But if the
in-kernel resource manager is used (/dev/tpmrm?), an -EINVAL errno code is
returned instead if the command isn't implemented. This confuses userspace
since it doesn't expect that error value.

This also isn't consistent with the behavior when not using TPM spaces and
accessing the TPM directly (/dev/tpm?). In this case, the command is sent
to the TPM even when not implemented and the TPM responds with an error.

Instead of returning an -EINVAL errno code when the tpm_validate_command()
function fails, synthesize a TPM command response so user-space can get a
TPM_RC_COMMAND_CODE as expected when a chip doesn't implement the command.

The TPM only sets 12 of the 32 bits in the TPM_RC response, so the TSS and
TAB specifications define that higher layers in the stack should use some
of the unused 20 bits to specify from which level of the stack the error
is coming from.

Since the TPM_RC_COMMAND_CODE response code is sent by the kernel resource
manager, set the error level to the TAB/RM layer so user-space is aware of
this.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: William Roberts <william.c.roberts@intel.com>
Reviewed-by: Philip Tricca <philip.b.tricca@intel.com>
Reviewed-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen  <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 2d5466a72e40..0b5b499f726a 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -93,12 +93,17 @@ enum tpm2_structures {
 	TPM2_ST_SESSIONS	= 0x8002,
 };
 
+/* Indicates from what layer of the software stack the error comes from */
+#define TSS2_RC_LAYER_SHIFT	 16
+#define TSS2_RESMGR_TPM_RC_LAYER (11 << TSS2_RC_LAYER_SHIFT)
+
 enum tpm2_return_codes {
 	TPM2_RC_SUCCESS		= 0x0000,
 	TPM2_RC_HASH		= 0x0083, /* RC_FMT1 */
 	TPM2_RC_HANDLE		= 0x008B,
 	TPM2_RC_INITIALIZE	= 0x0100, /* RC_VER1 */
 	TPM2_RC_DISABLED	= 0x0120,
+	TPM2_RC_COMMAND_CODE    = 0x0143,
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 };