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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
        "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
        David Howells <dhowells@redhat.com>,
        Kent Yoder <key@linux.vnet.ibm.com>,
        Jarkko Sakkinen <jarkko@kernel.org>
Subject: [PATCH 5.10 528/663] KEYS: trusted: Fix incorrect handling of tpm_get_random()
Date:   Mon,  1 Mar 2021 17:12:56 +0100
Message-Id: <20210301161207.969230242@linuxfoundation.org>
In-Reply-To: <20210301161141.760350206@linuxfoundation.org>
References: <20210301161141.760350206@linuxfoundation.org>
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From: Jarkko Sakkinen <jarkko@kernel.org>

commit 5df16caada3fba3b21cb09b85cdedf99507f4ec1 upstream.

When tpm_get_random() was introduced, it defined the following API for the
return value:

1. A positive value tells how many bytes of random data was generated.
2. A negative value on error.

However, in the call sites the API was used incorrectly, i.e. as it would
only return negative values and otherwise zero. Returning he positive read
counts to the user space does not make any possible sense.

Fix this by returning -EIO when tpm_get_random() returns a positive value.

Fixes: 41ab999c80f1 ("tpm: Move tpm_get_random api into the TPM device driver")
Cc: stable@vger.kernel.org
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Kent Yoder <key@linux.vnet.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 security/keys/trusted-keys/trusted_tpm1.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -403,9 +403,12 @@ static int osap(struct tpm_buf *tb, stru
 	int ret;
 
 	ret = tpm_get_random(chip, ononce, TPM_NONCE_SIZE);
-	if (ret != TPM_NONCE_SIZE)
+	if (ret < 0)
 		return ret;
 
+	if (ret != TPM_NONCE_SIZE)
+		return -EIO;
+
 	tpm_buf_reset(tb, TPM_TAG_RQU_COMMAND, TPM_ORD_OSAP);
 	tpm_buf_append_u16(tb, type);
 	tpm_buf_append_u32(tb, handle);
@@ -496,8 +499,12 @@ static int tpm_seal(struct tpm_buf *tb,
 		goto out;
 
 	ret = tpm_get_random(chip, td->nonceodd, TPM_NONCE_SIZE);
+	if (ret < 0)
+		return ret;
+
 	if (ret != TPM_NONCE_SIZE)
-		goto out;
+		return -EIO;
+
 	ordinal = htonl(TPM_ORD_SEAL);
 	datsize = htonl(datalen);
 	pcrsize = htonl(pcrinfosize);
@@ -601,9 +608,12 @@ static int tpm_unseal(struct tpm_buf *tb
 
 	ordinal = htonl(TPM_ORD_UNSEAL);
 	ret = tpm_get_random(chip, nonceodd, TPM_NONCE_SIZE);
+	if (ret < 0)
+		return ret;
+
 	if (ret != TPM_NONCE_SIZE) {
 		pr_info("trusted_key: tpm_get_random failed (%d)\n", ret);
-		return ret;
+		return -EIO;
 	}
 	ret = TSS_authhmac(authdata1, keyauth, TPM_NONCE_SIZE,
 			   enonce1, nonceodd, cont, sizeof(uint32_t),
@@ -1013,8 +1023,12 @@ static int trusted_instantiate(struct ke
 	case Opt_new:
 		key_len = payload->key_len;
 		ret = tpm_get_random(chip, payload->key, key_len);
+		if (ret < 0)
+			goto out;
+
 		if (ret != key_len) {
 			pr_info("trusted_key: key_create failed (%d)\n", ret);
+			ret = -EIO;
 			goto out;
 		}
 		if (tpm2)