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.

Link: http://lkml.kernel.org/r/20200616154311.12314-3-longman@redhat.com
Suggested-by: Joe Perches <joe@perches.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Waiman Long <longman@redhat.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

1 files changed, 3 insertions, 3 deletions

diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index d31031de51bc..6c992eb5c72f 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -199,7 +199,7 @@ static int pkcs1pad_encrypt_sign_complete(struct akcipher_request *req, int err)
 	sg_copy_from_buffer(req->dst,
 			    sg_nents_for_len(req->dst, ctx->key_size),
 			    out_buf, ctx->key_size);
-	kzfree(out_buf);
+	kfree_sensitive(out_buf);
 
 out:
 	req->dst_len = ctx->key_size;
@@ -322,7 +322,7 @@ static int pkcs1pad_decrypt_complete(struct akcipher_request *req, int err)
 				out_buf + pos, req->dst_len);
 
 done:
-	kzfree(req_ctx->out_buf);
+	kfree_sensitive(req_ctx->out_buf);
 
 	return err;
 }
@@ -500,7 +500,7 @@ static int pkcs1pad_verify_complete(struct akcipher_request *req, int err)
 		   req->dst_len) != 0)
 		err = -EKEYREJECTED;
 done:
-	kzfree(req_ctx->out_buf);
+	kfree_sensitive(req_ctx->out_buf);
 
 	return err;
 }