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>

2 files changed, 3 insertions, 3 deletions

diff --git a/arch/s390/crypto/prng.c b/arch/s390/crypto/prng.c
index e1ae23911ccd..5057773f82e9 100644
--- a/arch/s390/crypto/prng.c
+++ b/arch/s390/crypto/prng.c
@@ -249,7 +249,7 @@ static void prng_tdes_deinstantiate(void)
 {
 	pr_debug("The prng module stopped "
 		 "after running in triple DES mode\n");
-	kzfree(prng_data);
+	kfree_sensitive(prng_data);
 }
 
 
@@ -442,7 +442,7 @@ outfree:
 static void prng_sha512_deinstantiate(void)
 {
 	pr_debug("The prng module stopped after running in SHA-512 mode\n");
-	kzfree(prng_data);
+	kfree_sensitive(prng_data);
 }
 
 
diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
index d147f1b2c925..cd3914fc9f3d 100644
--- a/arch/x86/power/hibernate.c
+++ b/arch/x86/power/hibernate.c
@@ -98,7 +98,7 @@ static int get_e820_md5(struct e820_table *table, void *buf)
 	if (crypto_shash_digest(desc, (u8 *)table, size, buf))
 		ret = -EINVAL;
 
-	kzfree(desc);
+	kfree_sensitive(desc);
 
 free_tfm:
 	crypto_free_shash(tfm);