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, 5 insertions, 5 deletions

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 8d80d93cab97..e99fe34cfa00 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1218,19 +1218,19 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg)
 {
 	if (!drbg)
 		return;
-	kzfree(drbg->Vbuf);
+	kfree_sensitive(drbg->Vbuf);
 	drbg->Vbuf = NULL;
 	drbg->V = NULL;
-	kzfree(drbg->Cbuf);
+	kfree_sensitive(drbg->Cbuf);
 	drbg->Cbuf = NULL;
 	drbg->C = NULL;
-	kzfree(drbg->scratchpadbuf);
+	kfree_sensitive(drbg->scratchpadbuf);
 	drbg->scratchpadbuf = NULL;
 	drbg->reseed_ctr = 0;
 	drbg->d_ops = NULL;
 	drbg->core = NULL;
 	if (IS_ENABLED(CONFIG_CRYPTO_FIPS)) {
-		kzfree(drbg->prev);
+		kfree_sensitive(drbg->prev);
 		drbg->prev = NULL;
 		drbg->fips_primed = false;
 	}
@@ -1701,7 +1701,7 @@ static int drbg_fini_hash_kernel(struct drbg_state *drbg)
 	struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;
 	if (sdesc) {
 		crypto_free_shash(sdesc->shash.tfm);
-		kzfree(sdesc);
+		kfree_sensitive(sdesc);
 	}
 	drbg->priv_data = NULL;
 	return 0;