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>

4 files changed, 11 insertions, 11 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 874a551f339c..9daa256f69d4 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -797,7 +797,7 @@ calc_seckey(struct cifs_ses *ses)
 	ses->auth_key.len = CIFS_SESS_KEY_SIZE;
 
 	memzero_explicit(sec_key, CIFS_SESS_KEY_SIZE);
-	kzfree(ctx_arc4);
+	kfree_sensitive(ctx_arc4);
 	return 0;
 }
 
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a61abde09ffe..889fee586d94 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2182,7 +2182,7 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			tmp_end++;
 			if (!(tmp_end < end && tmp_end[1] == delim)) {
 				/* No it is not. Set the password to NULL */
-				kzfree(vol->password);
+				kfree_sensitive(vol->password);
 				vol->password = NULL;
 				break;
 			}
@@ -2220,7 +2220,7 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 					options = end;
 			}
 
-			kzfree(vol->password);
+			kfree_sensitive(vol->password);
 			/* Now build new password string */
 			temp_len = strlen(value);
 			vol->password = kzalloc(temp_len+1, GFP_KERNEL);
@@ -3198,7 +3198,7 @@ cifs_set_cifscreds(struct smb_vol *vol, struct cifs_ses *ses)
 			rc = -ENOMEM;
 			kfree(vol->username);
 			vol->username = NULL;
-			kzfree(vol->password);
+			kfree_sensitive(vol->password);
 			vol->password = NULL;
 			goto out_key_put;
 		}
@@ -4219,7 +4219,7 @@ void
 cifs_cleanup_volume_info_contents(struct smb_vol *volume_info)
 {
 	kfree(volume_info->username);
-	kzfree(volume_info->password);
+	kfree_sensitive(volume_info->password);
 	kfree(volume_info->UNC);
 	kfree(volume_info->domainname);
 	kfree(volume_info->iocharset);
@@ -5345,7 +5345,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 
 out:
 	kfree(vol_info->username);
-	kzfree(vol_info->password);
+	kfree_sensitive(vol_info->password);
 	kfree(vol_info);
 
 	return tcon;
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index df81c718d2fa..7a8d41493aad 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1131,7 +1131,7 @@ err_free_domainname:
 err_free_unc:
 	kfree(new->UNC);
 err_free_password:
-	kzfree(new->password);
+	kfree_sensitive(new->password);
 err_free_username:
 	kfree(new->username);
 	kfree(new);
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index e44d049142d0..3e3772446c71 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -103,12 +103,12 @@ sesInfoFree(struct cifs_ses *buf_to_free)
 	kfree(buf_to_free->serverOS);
 	kfree(buf_to_free->serverDomain);
 	kfree(buf_to_free->serverNOS);
-	kzfree(buf_to_free->password);
+	kfree_sensitive(buf_to_free->password);
 	kfree(buf_to_free->user_name);
 	kfree(buf_to_free->domainName);
-	kzfree(buf_to_free->auth_key.response);
+	kfree_sensitive(buf_to_free->auth_key.response);
 	kfree(buf_to_free->iface_list);
-	kzfree(buf_to_free);
+	kfree_sensitive(buf_to_free);
 }
 
 struct cifs_tcon *
@@ -148,7 +148,7 @@ tconInfoFree(struct cifs_tcon *buf_to_free)
 	}
 	atomic_dec(&tconInfoAllocCount);
 	kfree(buf_to_free->nativeFileSystem);
-	kzfree(buf_to_free->password);
+	kfree_sensitive(buf_to_free->password);
 	kfree(buf_to_free->crfid.fid);
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	kfree(buf_to_free->dfs_path);