Bluetooth: allocate data for kpp on heap

Bluetooth would crash when computing ECDH keys with kpp
if VMAP_STACK is enabled. Fix by allocating data passed
to kpp on heap.

Fixes: 58771c1c ("Bluetooth: convert smp and selftest to crypto kpp
API")
Signed-off-by: Salvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/ecdh_helper.c

@@ -59,16 +59,19 @@ bool compute_ecdh_secret(const u8 public_key[64], const u8 private_key[32],
 	struct ecdh p;
 	struct ecdh_completion result;
 	struct scatterlist src, dst;
-	u8 tmp[64];
-	u8 *buf;
+	u8 *tmp, *buf;
 	unsigned int buf_len;
 	int err = -ENOMEM;
 
+	tmp = kmalloc(64, GFP_KERNEL);
+	if (!tmp)
+		return false;
+
 	tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0);
 	if (IS_ERR(tfm)) {
 		pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n",
 		       PTR_ERR(tfm));
-		return false;
+		goto free_tmp;
 	}
 
 	req = kpp_request_alloc(tfm, GFP_KERNEL);
@@ -128,6 +131,8 @@ free_req:
 	kpp_request_free(req);
 free_kpp:
 	crypto_free_kpp(tfm);
+free_tmp:
+	kfree(tmp);
 	return (err == 0);
 }
 
@@ -138,18 +143,21 @@ bool generate_ecdh_keys(u8 public_key[64], u8 private_key[32])
 	struct ecdh p;
 	struct ecdh_completion result;
 	struct scatterlist dst;
-	u8 tmp[64];
-	u8 *buf;
+	u8 *tmp, *buf;
 	unsigned int buf_len;
 	int err = -ENOMEM;
 	const unsigned short max_tries = 16;
 	unsigned short tries = 0;
 
+	tmp = kmalloc(64, GFP_KERNEL);
+	if (!tmp)
+		return false;
+
 	tfm = crypto_alloc_kpp("ecdh", CRYPTO_ALG_INTERNAL, 0);
 	if (IS_ERR(tfm)) {
 		pr_err("alg: kpp: Failed to load tfm for kpp: %ld\n",
 		       PTR_ERR(tfm));
-		return false;
+		goto free_tmp;
 	}
 
 	req = kpp_request_alloc(tfm, GFP_KERNEL);
@@ -219,5 +227,7 @@ free_req:
 	kpp_request_free(req);
 free_kpp:
 	crypto_free_kpp(tfm);
+free_tmp:
+	kfree(tmp);
 	return (err == 0);
 }

net/bluetooth/selftest.c

@@ -142,18 +142,30 @@ static int __init test_ecdh_sample(const u8 priv_a[32], const u8 priv_b[32],
 				   const u8 pub_a[64], const u8 pub_b[64],
 				   const u8 dhkey[32])
 {
-	u8 dhkey_a[32], dhkey_b[32];
+	u8 *tmp, *dhkey_a, *dhkey_b;
+	int ret = 0;
+
+	tmp = kmalloc(64, GFP_KERNEL);
+	if (!tmp)
+		return -EINVAL;
+
+	dhkey_a = &tmp[0];
+	dhkey_b = &tmp[32];
 
 	compute_ecdh_secret(pub_b, priv_a, dhkey_a);
 	compute_ecdh_secret(pub_a, priv_b, dhkey_b);
 
-	if (memcmp(dhkey_a, dhkey, 32))
-		return -EINVAL;
+	if (memcmp(dhkey_a, dhkey, 32)) {
+		ret = -EINVAL;
+		goto out;
+	}
 
 	if (memcmp(dhkey_b, dhkey, 32))
-		return -EINVAL;
+		ret = -EINVAL;
 
-	return 0;
+out:
+	kfree(dhkey_a);
+	return ret;
 }
 
 static char test_ecdh_buffer[32];