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, 7 insertions, 7 deletions

diff --git a/security/keys/dh.c b/security/keys/dh.c
index c4c629bb1c03..1abfa70ed6e1 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -58,9 +58,9 @@ error:
 
 static void dh_free_data(struct dh *dh)
 {
-	kzfree(dh->key);
-	kzfree(dh->p);
-	kzfree(dh->g);
+	kfree_sensitive(dh->key);
+	kfree_sensitive(dh->p);
+	kfree_sensitive(dh->g);
 }
 
 struct dh_completion {
@@ -126,7 +126,7 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
 	if (sdesc->shash.tfm)
 		crypto_free_shash(sdesc->shash.tfm);
 
-	kzfree(sdesc);
+	kfree_sensitive(sdesc);
 }
 
 /*
@@ -220,7 +220,7 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
 		ret = -EFAULT;
 
 err:
-	kzfree(outbuf);
+	kfree_sensitive(outbuf);
 	return ret;
 }
 
@@ -395,11 +395,11 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
 out6:
 	kpp_request_free(req);
 out5:
-	kzfree(outbuf);
+	kfree_sensitive(outbuf);
 out4:
 	crypto_free_kpp(tfm);
 out3:
-	kzfree(secret);
+	kfree_sensitive(secret);
 out2:
 	dh_free_data(&dh_inputs);
 out1: