linux-kernel - [PATCH 4.19 47/73] evm: check hash algorithm passed to init

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Date:   Fri,  7 Jun 2019 17:39:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>,
        Mimi Zohar <zohar@...ux.ibm.com>
Subject: [PATCH 4.19 47/73] evm: check hash algorithm passed to init_desc()

From: Roberto Sassu <roberto.sassu@...wei.com>

commit 221be106d75c1b511973301542f47d6000d0b63e upstream.

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@...wei.com>
Cc: stable@...r.kernel.org
Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/integrity/evm/evm_crypto.c |    3 +++
 1 file changed, 3 insertions(+)

--- 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
 		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];
 	}