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>

2 files changed, 7 insertions, 7 deletions

diff --git a/drivers/crypto/virtio/virtio_crypto_algs.c b/drivers/crypto/virtio/virtio_crypto_algs.c
index b2601958282e..583c0b535d13 100644
--- a/drivers/crypto/virtio/virtio_crypto_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_algs.c
@@ -167,7 +167,7 @@ static int virtio_crypto_alg_skcipher_init_session(
 				num_in, vcrypto, GFP_ATOMIC);
 	if (err < 0) {
 		spin_unlock(&vcrypto->ctrl_lock);
-		kzfree(cipher_key);
+		kfree_sensitive(cipher_key);
 		return err;
 	}
 	virtqueue_kick(vcrypto->ctrl_vq);
@@ -184,7 +184,7 @@ static int virtio_crypto_alg_skcipher_init_session(
 		spin_unlock(&vcrypto->ctrl_lock);
 		pr_err("virtio_crypto: Create session failed status: %u\n",
 			le32_to_cpu(vcrypto->input.status));
-		kzfree(cipher_key);
+		kfree_sensitive(cipher_key);
 		return -EINVAL;
 	}
 
@@ -197,7 +197,7 @@ static int virtio_crypto_alg_skcipher_init_session(
 
 	spin_unlock(&vcrypto->ctrl_lock);
 
-	kzfree(cipher_key);
+	kfree_sensitive(cipher_key);
 	return 0;
 }
 
@@ -472,9 +472,9 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
 	return 0;
 
 free_iv:
-	kzfree(iv);
+	kfree_sensitive(iv);
 free:
-	kzfree(req_data);
+	kfree_sensitive(req_data);
 	kfree(sgs);
 	return err;
 }
@@ -583,7 +583,7 @@ static void virtio_crypto_skcipher_finalize_req(
 		scatterwalk_map_and_copy(req->iv, req->dst,
 					 req->cryptlen - AES_BLOCK_SIZE,
 					 AES_BLOCK_SIZE, 0);
-	kzfree(vc_sym_req->iv);
+	kfree_sensitive(vc_sym_req->iv);
 	virtcrypto_clear_request(&vc_sym_req->base);
 
 	crypto_finalize_skcipher_request(vc_sym_req->base.dataq->engine,
diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
index 77e744eaedd0..0c66d6193ca2 100644
--- a/drivers/crypto/virtio/virtio_crypto_core.c
+++ b/drivers/crypto/virtio/virtio_crypto_core.c
@@ -17,7 +17,7 @@ void
 virtcrypto_clear_request(struct virtio_crypto_request *vc_req)
 {
 	if (vc_req) {
-		kzfree(vc_req->req_data);
+		kfree_sensitive(vc_req->req_data);
 		kfree(vc_req->sgs);
 	}
 }