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>

8 files changed, 10 insertions, 8 deletions

diff --git a/include/crypto/aead.h b/include/crypto/aead.h
index 62c68550aab6..c32a6f5664e9 100644
--- a/include/crypto/aead.h
+++ b/include/crypto/aead.h
@@ -425,7 +425,7 @@ static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
  */
 static inline void aead_request_free(struct aead_request *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 /**
diff --git a/include/crypto/akcipher.h b/include/crypto/akcipher.h
index 6924b091adec..1d3aa252caba 100644
--- a/include/crypto/akcipher.h
+++ b/include/crypto/akcipher.h
@@ -207,7 +207,7 @@ static inline struct akcipher_request *akcipher_request_alloc(
  */
 static inline void akcipher_request_free(struct akcipher_request *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 /**
diff --git a/include/crypto/gf128mul.h b/include/crypto/gf128mul.h
index fa0a63d298dc..81330c6446f6 100644
--- a/include/crypto/gf128mul.h
+++ b/include/crypto/gf128mul.h
@@ -230,7 +230,7 @@ void gf128mul_4k_bbe(be128 *a, const struct gf128mul_4k *t);
 void gf128mul_x8_ble(le128 *r, const le128 *x);
 static inline void gf128mul_free_4k(struct gf128mul_4k *t)
 {
-	kzfree(t);
+	kfree_sensitive(t);
 }
 
 
diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 19ce91f2359f..0d1b403888c9 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -606,7 +606,7 @@ static inline struct ahash_request *ahash_request_alloc(
  */
 static inline void ahash_request_free(struct ahash_request *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 static inline void ahash_request_zero(struct ahash_request *req)
diff --git a/include/crypto/internal/acompress.h b/include/crypto/internal/acompress.h
index cf478681b53e..cfc47e18820f 100644
--- a/include/crypto/internal/acompress.h
+++ b/include/crypto/internal/acompress.h
@@ -46,7 +46,7 @@ static inline struct acomp_req *__acomp_request_alloc(struct crypto_acomp *tfm)
 
 static inline void __acomp_request_free(struct acomp_req *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 /**
diff --git a/include/crypto/kpp.h b/include/crypto/kpp.h
index cd9a9b500624..88b591215d5c 100644
--- a/include/crypto/kpp.h
+++ b/include/crypto/kpp.h
@@ -187,7 +187,7 @@ static inline struct kpp_request *kpp_request_alloc(struct crypto_kpp *tfm,
  */
 static inline void kpp_request_free(struct kpp_request *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 /**
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index 5663f71198b3..6a733b171a5d 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -508,7 +508,7 @@ static inline struct skcipher_request *skcipher_request_alloc(
  */
 static inline void skcipher_request_free(struct skcipher_request *req)
 {
-	kzfree(req);
+	kfree_sensitive(req);
 }
 
 static inline void skcipher_request_zero(struct skcipher_request *req)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 6d454886bcaf..0884d82c55ee 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -186,10 +186,12 @@ void memcg_deactivate_kmem_caches(struct mem_cgroup *, struct mem_cgroup *);
  */
 void * __must_check krealloc(const void *, size_t, gfp_t);
 void kfree(const void *);
-void kzfree(const void *);
+void kfree_sensitive(const void *);
 size_t __ksize(const void *);
 size_t ksize(const void *);
 
+#define kzfree(x)	kfree_sensitive(x)	/* For backward compatibility */
+
 #ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
 void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 			bool to_user);