[PATCH 4.17 081/220] tpm: fix use after free in tpm2_load_context()

[Greg Kroah-Hartman]

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

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

From: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>

commit 8c81c24758ffbf17cf06c6835d361ffa57be2f0e upstream.

If load context command returns with TPM2_RC_HANDLE or TPM2_RC_REFERENCE_H0
then we have use after free in line 114 and double free in 117.

Fixes: 4d57856a21ed2 ("tpm2: add session handle context saving and restoring to the space code")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off--by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/tpm/tpm2-space.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -102,8 +102,9 @@ static int tpm2_load_context(struct tpm_
 		 * TPM_RC_REFERENCE_H0 means the session has been
 		 * flushed outside the space
 		 */
-		rc = -ENOENT;
+		*handle = 0;
 		tpm_buf_destroy(&tbuf);
+		return -ENOENT;
 	} else if (rc > 0) {
 		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
 			 __func__, rc);