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.

[[email protected]: fs/crypto/inline_crypt.c needs linux/slab.h]
[[email protected]: fix fs/crypto/inline_crypt.c some more]

Suggested-by: Joe Perches <[email protected]>
Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: David Howells <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: James Morris <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: "Jason A . Donenfeld" <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
index b6b8574caa13..faa25541ccb6 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -16,6 +16,7 @@
 #include <linux/blkdev.h>
 #include <linux/buffer_head.h>
 #include <linux/sched/mm.h>
+#include <linux/slab.h>
 
 #include "fscrypt_private.h"
 
@@ -187,7 +188,7 @@ int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
 fail:
 	for (i = 0; i < queue_refs; i++)
 		blk_put_queue(blk_key->devs[i]);
-	kzfree(blk_key);
+	kfree_sensitive(blk_key);
 	return err;
 }
 
@@ -201,7 +202,7 @@ void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
 			blk_crypto_evict_key(blk_key->devs[i], &blk_key->base);
 			blk_put_queue(blk_key->devs[i]);
 		}
-		kzfree(blk_key);
+		kfree_sensitive(blk_key);
 	}
 }