[PATCH 4.9 004/103] tpm: fix RC value check in tpm2_seal_trusted

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

commit 7d761119a914ec0ac05ec2a5378d1f86e680967d upstream.

The error code handling is broken as any error code that has the same
bits set as TPM_RC_HASH passes. Implemented tpm2_rc_value() helper to
parse the error value from FMT0 and FMT1 error codes so that these types
of mistakes are prevented in the future.

Fixes: 5ca4c20cfd37 ("keys, trusted: select hash algorithm for TPM2 chips")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/tpm/tpm.h      |    5 +++++
 drivers/char/tpm/tpm2-cmd.c |    2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -518,6 +518,11 @@ static inline void tpm_add_ppi(struct tp
 }
 #endif
 
+static inline inline u32 tpm2_rc_value(u32 rc)
+{
+	return (rc & BIT(7)) ? rc & 0xff : rc;
+}
+
 int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
 int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash);
 int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -529,7 +529,7 @@ out:
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0) {
-		if ((rc & TPM2_RC_HASH) == TPM2_RC_HASH)
+		if (tpm2_rc_value(rc) == TPM2_RC_HASH)
 			rc = -EINVAL;
 		else
 			rc = -EPERM;