evm: check hash algorithm passed to init_desc()

commit 221be10 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: 5feeb61 ("evm: Allow non-SHA1 digital signatures") Signed-off-by: Roberto Sassu <[email protected]> Cc: [email protected] Signed-off-by: Mimi Zohar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
coreos · Jun 9, 2019 · 6e322a9 · 6e322a9
1 parent f85b87a
commit 6e322a9
Showing 1 changed file with 3 additions and 0 deletions.
diff --git 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];
 	}