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>

3 files changed, 6 insertions, 6 deletions

diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c
index e7180da1fc6a..794fb3001880 100644
--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -1003,7 +1003,7 @@ krb5_rc4_setup_seq_key(struct krb5_ctx *kctx,
 	err = 0;
 
 out_err:
-	kzfree(desc);
+	kfree_sensitive(desc);
 	crypto_free_shash(hmac);
 	dprintk("%s: returning %d\n", __func__, err);
 	return err;
@@ -1079,7 +1079,7 @@ krb5_rc4_setup_enc_key(struct krb5_ctx *kctx,
 	err = 0;
 
 out_err:
-	kzfree(desc);
+	kfree_sensitive(desc);
 	crypto_free_shash(hmac);
 	dprintk("%s: returning %d\n", __func__, err);
 	return err;
diff --git a/net/sunrpc/auth_gss/gss_krb5_keys.c b/net/sunrpc/auth_gss/gss_krb5_keys.c
index 3b7f721c023b..726c076950c0 100644
--- a/net/sunrpc/auth_gss/gss_krb5_keys.c
+++ b/net/sunrpc/auth_gss/gss_krb5_keys.c
@@ -228,11 +228,11 @@ u32 krb5_derive_key(const struct gss_krb5_enctype *gk5e,
 	ret = 0;
 
 err_free_raw:
-	kzfree(rawkey);
+	kfree_sensitive(rawkey);
 err_free_out:
-	kzfree(outblockdata);
+	kfree_sensitive(outblockdata);
 err_free_in:
-	kzfree(inblockdata);
+	kfree_sensitive(inblockdata);
 err_free_cipher:
 	crypto_free_sync_skcipher(cipher);
 err_return:
diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c
index 75b3c2e9e8f8..a84a5b289484 100644
--- a/net/sunrpc/auth_gss/gss_krb5_mech.c
+++ b/net/sunrpc/auth_gss/gss_krb5_mech.c
@@ -443,7 +443,7 @@ context_derive_keys_rc4(struct krb5_ctx *ctx)
 	desc->tfm = hmac;
 
 	err = crypto_shash_digest(desc, sigkeyconstant, slen, ctx->cksum);
-	kzfree(desc);
+	kfree_sensitive(desc);
 	if (err)
 		goto out_err_free_hmac;
 	/*