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>

1 files changed, 7 insertions, 7 deletions

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 14cf81d1a30b..deebbf14eeca 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/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 = {