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From:   Roberto Sassu <roberto.sassu@huawei.com>
To:     <zohar@linux.ibm.com>, <dmitry.kasatkin@huawei.com>,
        <mjg59@google.com>
CC:     <linux-integrity@vger.kernel.org>,
        <linux-security-module@vger.kernel.org>,
        <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <silviu.vlasceanu@huawei.com>,
        Roberto Sassu <roberto.sassu@huawei.com>,
        <stable@vger.kernel.org>
Subject: [PATCH v2 1/3] evm: check hash algorithm passed to init_desc()
Date:   Wed, 29 May 2019 15:30:33 +0200
Message-ID: <20190529133035.28724-2-roberto.sassu@huawei.com>
In-Reply-To: <20190529133035.28724-1-roberto.sassu@huawei.com>
References: <20190529133035.28724-1-roberto.sassu@huawei.com>
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This patch prevents memory access beyond the evm_tfm array by checking the
validity of the index (hash algorithm) passed to init_desc(). The hash
algorithm can be arbitrarily set if the security.ima xattr type is not
EVM_XATTR_HMAC.

Fixes: 5feeb61183dde ("evm: Allow non-SHA1 digital signatures")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Cc: stable@vger.kernel.org
---
 security/integrity/evm/evm_crypto.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index e11564eb645b..82a38e801ee4 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -89,6 +89,9 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
 		tfm = &hmac_tfm;
 		algo = evm_hmac;
 	} else {
+		if (hash_algo >= HASH_ALGO__LAST)
+			return ERR_PTR(-EINVAL);
+
 		tfm = &evm_tfm[hash_algo];
 		algo = hash_algo_name[hash_algo];
 	}
-- 
2.17.1