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, 3 insertions, 3 deletions

diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index dd708e8f13c0..691347dea3c1 100644
--- a/security/keys/big_key.c
+++ b/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;
 }