mm, treewide: rename kzfree() to kfree_sensitive()

As said by Linus:

  A symmetric naming is only helpful if it implies symmetries in use.
  Otherwise it's actively misleading.

  In "kzalloc()", the z is meaningful and an important part of what the
  caller wants.

  In "kzfree()", the z is actively detrimental, because maybe in the
  future we really _might_ want to use that "memfill(0xdeadbeef)" or
  something. The "zero" part of the interface isn't even _relevant_.

The main reason that kzfree() exists is to clear sensitive information
that should not be leaked to other future users of the same memory
objects.

Rename kzfree() to kfree_sensitive() to follow the example of the recently
added kvfree_sensitive() and make the intention of the API more explicit.
In addition, memzero_explicit() is used to clear the memory to make sure
that it won't get optimized away by the compiler.

The renaming is done by using the command sequence:

  git grep -w --name-only kzfree |\
  xargs sed -i 's/kzfree/kfree_sensitive/'

followed by some editing of the kfree_sensitive() kerneldoc and adding
a kzfree backward compatibility macro in slab.h.

[akpm@linux-foundation.org: fs/crypto/inline_crypt.c needs linux/slab.h]
[akpm@linux-foundation.org: fix fs/crypto/inline_crypt.c some more]

Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Joe Perches <joe@perches.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Jason A . Donenfeld" <Jason@zx2c4.com>
Link: http://lkml.kernel.org/r/20200616154311.12314-3-longman@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/keys/big_key.c

@@ -138,7 +138,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
 err_fput:
 	fput(file);
 err_enckey:
-	kzfree(enckey);
+	kfree_sensitive(enckey);
 error:
 	memzero_explicit(buf, enclen);
 	kvfree(buf);
@@ -155,7 +155,7 @@ void big_key_free_preparse(struct key_preparsed_payload *prep)
 
 		path_put(path);
 	}
-	kzfree(prep->payload.data[big_key_data]);
+	kfree_sensitive(prep->payload.data[big_key_data]);
 }
 
 /*
@@ -187,7 +187,7 @@ void big_key_destroy(struct key *key)
 		path->mnt = NULL;
 		path->dentry = NULL;
 	}
-	kzfree(key->payload.data[big_key_data]);
+	kfree_sensitive(key->payload.data[big_key_data]);
 	key->payload.data[big_key_data] = NULL;
 }
 

security/keys/dh.c

@@ -58,9 +58,9 @@ error:
 
 static void dh_free_data(struct dh *dh)
 {
-	kzfree(dh->key);
-	kzfree(dh->p);
-	kzfree(dh->g);
+	kfree_sensitive(dh->key);
+	kfree_sensitive(dh->p);
+	kfree_sensitive(dh->g);
 }
 
 struct dh_completion {
@@ -126,7 +126,7 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
 	if (sdesc->shash.tfm)
 		crypto_free_shash(sdesc->shash.tfm);
 
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 }
 
 /*
@@ -220,7 +220,7 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
 		ret = -EFAULT;
 
 err:
-	kzfree(outbuf);
+	kfree_sensitive(outbuf);
 	return ret;
 }
 
@@ -395,11 +395,11 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
 out6:
 	kpp_request_free(req);
 out5:
-	kzfree(outbuf);
+	kfree_sensitive(outbuf);
 out4:
 	crypto_free_kpp(tfm);
 out3:
-	kzfree(secret);
+	kfree_sensitive(secret);
 out2:
 	dh_free_data(&dh_inputs);
 out1:

security/keys/encrypted-keys/encrypted.c

@@ -370,7 +370,7 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 	       master_keylen);
 	ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
 				      derived_key);
-	kzfree(derived_buf);
+	kfree_sensitive(derived_buf);
 	return ret;
 }
 
@@ -812,13 +812,13 @@ static int encrypted_instantiate(struct key *key,
 	ret = encrypted_init(epayload, key->description, format, master_desc,
 			     decrypted_datalen, hex_encoded_iv);
 	if (ret < 0) {
-		kzfree(epayload);
+		kfree_sensitive(epayload);
 		goto out;
 	}
 
 	rcu_assign_keypointer(key, epayload);
 out:
-	kzfree(datablob);
+	kfree_sensitive(datablob);
 	return ret;
 }
 
@@ -827,7 +827,7 @@ static void encrypted_rcu_free(struct rcu_head *rcu)
 	struct encrypted_key_payload *epayload;
 
 	epayload = container_of(rcu, struct encrypted_key_payload, rcu);
-	kzfree(epayload);
+	kfree_sensitive(epayload);
 }
 
 /*
@@ -885,7 +885,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 	rcu_assign_keypointer(key, new_epayload);
 	call_rcu(&epayload->rcu, encrypted_rcu_free);
 out:
-	kzfree(buf);
+	kfree_sensitive(buf);
 	return ret;
 }
 
@@ -946,7 +946,7 @@ static long encrypted_read(const struct key *key, char *buffer,
 	memzero_explicit(derived_key, sizeof(derived_key));
 
 	memcpy(buffer, ascii_buf, asciiblob_len);
-	kzfree(ascii_buf);
+	kfree_sensitive(ascii_buf);
 
 	return asciiblob_len;
 out:
@@ -961,7 +961,7 @@ out:
  */
 static void encrypted_destroy(struct key *key)
 {
-	kzfree(key->payload.data[0]);
+	kfree_sensitive(key->payload.data[0]);
 }
 
 struct key_type key_type_encrypted = {

security/keys/trusted-keys/trusted_tpm1.c

@@ -68,7 +68,7 @@ static int TSS_sha1(const unsigned char *data, unsigned int datalen,
 	}
 
 	ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 	return ret;
 }
 
@@ -112,7 +112,7 @@ static int TSS_rawhmac(unsigned char *digest, const unsigned char *key,
 	if (!ret)
 		ret = crypto_shash_final(&sdesc->shash, digest);
 out:
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 	return ret;
 }
 
@@ -166,7 +166,7 @@ int TSS_authhmac(unsigned char *digest, const unsigned char *key,
 				  paramdigest, TPM_NONCE_SIZE, h1,
 				  TPM_NONCE_SIZE, h2, 1, &c, 0, 0);
 out:
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(TSS_authhmac);
@@ -251,7 +251,7 @@ int TSS_checkhmac1(unsigned char *buffer,
 	if (memcmp(testhmac, authdata, SHA1_DIGEST_SIZE))
 		ret = -EINVAL;
 out:
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(TSS_checkhmac1);
@@ -353,7 +353,7 @@ static int TSS_checkhmac2(unsigned char *buffer,
 	if (memcmp(testhmac2, authdata2, SHA1_DIGEST_SIZE))
 		ret = -EINVAL;
 out:
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 	return ret;
 }
 
@@ -563,7 +563,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
 		*bloblen = storedsize;
 	}
 out:
-	kzfree(td);
+	kfree_sensitive(td);
 	return ret;
 }
 
@@ -1031,12 +1031,12 @@ static int trusted_instantiate(struct key *key,
 	if (!ret && options->pcrlock)
 		ret = pcrlock(options->pcrlock);
 out:
-	kzfree(datablob);
-	kzfree(options);
+	kfree_sensitive(datablob);
+	kfree_sensitive(options);
 	if (!ret)
 		rcu_assign_keypointer(key, payload);
 	else
-		kzfree(payload);
+		kfree_sensitive(payload);
 	return ret;
 }
 
@@ -1045,7 +1045,7 @@ static void trusted_rcu_free(struct rcu_head *rcu)
 	struct trusted_key_payload *p;
 
 	p = container_of(rcu, struct trusted_key_payload, rcu);
-	kzfree(p);
+	kfree_sensitive(p);
 }
 
 /*
@@ -1087,13 +1087,13 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
 	ret = datablob_parse(datablob, new_p, new_o);
 	if (ret != Opt_update) {
 		ret = -EINVAL;
-		kzfree(new_p);
+		kfree_sensitive(new_p);
 		goto out;
 	}
 
 	if (!new_o->keyhandle) {
 		ret = -EINVAL;
-		kzfree(new_p);
+		kfree_sensitive(new_p);
 		goto out;
 	}
 
@@ -1107,22 +1107,22 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
 	ret = key_seal(new_p, new_o);
 	if (ret < 0) {
 		pr_info("trusted_key: key_seal failed (%d)\n", ret);
-		kzfree(new_p);
+		kfree_sensitive(new_p);
 		goto out;
 	}
 	if (new_o->pcrlock) {
 		ret = pcrlock(new_o->pcrlock);
 		if (ret < 0) {
 			pr_info("trusted_key: pcrlock failed (%d)\n", ret);
-			kzfree(new_p);
+			kfree_sensitive(new_p);
 			goto out;
 		}
 	}
 	rcu_assign_keypointer(key, new_p);
 	call_rcu(&p->rcu, trusted_rcu_free);
 out:
-	kzfree(datablob);
-	kzfree(new_o);
+	kfree_sensitive(datablob);
+	kfree_sensitive(new_o);
 	return ret;
 }
 
@@ -1154,7 +1154,7 @@ static long trusted_read(const struct key *key, char *buffer,
  */
 static void trusted_destroy(struct key *key)
 {
-	kzfree(key->payload.data[0]);
+	kfree_sensitive(key->payload.data[0]);
 }
 
 struct key_type key_type_trusted = {

security/keys/user_defined.c

@@ -82,7 +82,7 @@ EXPORT_SYMBOL_GPL(user_preparse);
  */
 void user_free_preparse(struct key_preparsed_payload *prep)
 {
-	kzfree(prep->payload.data[0]);
+	kfree_sensitive(prep->payload.data[0]);
 }
 EXPORT_SYMBOL_GPL(user_free_preparse);
 
@@ -91,7 +91,7 @@ static void user_free_payload_rcu(struct rcu_head *head)
 	struct user_key_payload *payload;
 
 	payload = container_of(head, struct user_key_payload, rcu);
-	kzfree(payload);
+	kfree_sensitive(payload);
 }
 
 /*
@@ -147,7 +147,7 @@ void user_destroy(struct key *key)
 {
 	struct user_key_payload *upayload = key->payload.data[0];
 
-	kzfree(upayload);
+	kfree_sensitive(upayload);
 }
 
 EXPORT_SYMBOL_GPL(user_destroy);