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, 15 insertions, 15 deletions

diff --git a/net/bluetooth/ecdh_helper.c b/net/bluetooth/ecdh_helper.c
index 2155ce802877..3226fe02e875 100644
--- a/net/bluetooth/ecdh_helper.c
+++ b/net/bluetooth/ecdh_helper.c
@@ -104,7 +104,7 @@ int compute_ecdh_secret(struct crypto_kpp *tfm, const u8 public_key[64],
 free_all:
 	kpp_request_free(req);
 free_tmp:
-	kzfree(tmp);
+	kfree_sensitive(tmp);
 	return err;
 }
 
@@ -151,9 +151,9 @@ int set_ecdh_privkey(struct crypto_kpp *tfm, const u8 private_key[32])
 	err = crypto_kpp_set_secret(tfm, buf, buf_len);
 	/* fall through */
 free_all:
-	kzfree(buf);
+	kfree_sensitive(buf);
 free_tmp:
-	kzfree(tmp);
+	kfree_sensitive(tmp);
 	return err;
 }
 
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 433227f96c73..bf4bef13d935 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -753,9 +753,9 @@ static void smp_chan_destroy(struct l2cap_conn *conn)
 	complete = test_bit(SMP_FLAG_COMPLETE, &smp->flags);
 	mgmt_smp_complete(hcon, complete);
 
-	kzfree(smp->csrk);
-	kzfree(smp->slave_csrk);
-	kzfree(smp->link_key);
+	kfree_sensitive(smp->csrk);
+	kfree_sensitive(smp->slave_csrk);
+	kfree_sensitive(smp->link_key);
 
 	crypto_free_shash(smp->tfm_cmac);
 	crypto_free_kpp(smp->tfm_ecdh);
@@ -789,7 +789,7 @@ static void smp_chan_destroy(struct l2cap_conn *conn)
 	}
 
 	chan->data = NULL;
-	kzfree(smp);
+	kfree_sensitive(smp);
 	hci_conn_drop(hcon);
 }
 
@@ -1156,7 +1156,7 @@ static void sc_generate_link_key(struct smp_chan *smp)
 		const u8 salt[16] = { 0x31, 0x70, 0x6d, 0x74 };
 
 		if (smp_h7(smp->tfm_cmac, smp->tk, salt, smp->link_key)) {
-			kzfree(smp->link_key);
+			kfree_sensitive(smp->link_key);
 			smp->link_key = NULL;
 			return;
 		}
@@ -1165,14 +1165,14 @@ static void sc_generate_link_key(struct smp_chan *smp)
 		const u8 tmp1[4] = { 0x31, 0x70, 0x6d, 0x74 };
 
 		if (smp_h6(smp->tfm_cmac, smp->tk, tmp1, smp->link_key)) {
-			kzfree(smp->link_key);
+			kfree_sensitive(smp->link_key);
 			smp->link_key = NULL;
 			return;
 		}
 	}
 
 	if (smp_h6(smp->tfm_cmac, smp->link_key, lebr, smp->link_key)) {
-		kzfree(smp->link_key);
+		kfree_sensitive(smp->link_key);
 		smp->link_key = NULL;
 		return;
 	}
@@ -1407,7 +1407,7 @@ static struct smp_chan *smp_chan_create(struct l2cap_conn *conn)
 free_shash:
 	crypto_free_shash(smp->tfm_cmac);
 zfree_smp:
-	kzfree(smp);
+	kfree_sensitive(smp);
 	return NULL;
 }
 
@@ -3278,7 +3278,7 @@ static struct l2cap_chan *smp_add_cid(struct hci_dev *hdev, u16 cid)
 	tfm_cmac = crypto_alloc_shash("cmac(aes)", 0, 0);
 	if (IS_ERR(tfm_cmac)) {
 		BT_ERR("Unable to create CMAC crypto context");
-		kzfree(smp);
+		kfree_sensitive(smp);
 		return ERR_CAST(tfm_cmac);
 	}
 
@@ -3286,7 +3286,7 @@ static struct l2cap_chan *smp_add_cid(struct hci_dev *hdev, u16 cid)
 	if (IS_ERR(tfm_ecdh)) {
 		BT_ERR("Unable to create ECDH crypto context");
 		crypto_free_shash(tfm_cmac);
-		kzfree(smp);
+		kfree_sensitive(smp);
 		return ERR_CAST(tfm_ecdh);
 	}
 
@@ -3300,7 +3300,7 @@ create_chan:
 		if (smp) {
 			crypto_free_shash(smp->tfm_cmac);
 			crypto_free_kpp(smp->tfm_ecdh);
-			kzfree(smp);
+			kfree_sensitive(smp);
 		}
 		return ERR_PTR(-ENOMEM);
 	}
@@ -3347,7 +3347,7 @@ static void smp_del_chan(struct l2cap_chan *chan)
 		chan->data = NULL;
 		crypto_free_shash(smp->tfm_cmac);
 		crypto_free_kpp(smp->tfm_ecdh);
-		kzfree(smp);
+		kfree_sensitive(smp);
 	}
 
 	l2cap_chan_put(chan);