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, 3 insertions, 3 deletions

diff --git a/drivers/misc/ibmvmc.c b/drivers/misc/ibmvmc.c
index c0d139c26505..2d778d0f011e 100644
--- a/drivers/misc/ibmvmc.c
+++ b/drivers/misc/ibmvmc.c
@@ -286,7 +286,7 @@ static void *alloc_dma_buffer(struct vio_dev *vdev, size_t size,
 
 	if (dma_mapping_error(&vdev->dev, *dma_handle)) {
 		*dma_handle = 0;
-		kzfree(buffer);
+		kfree_sensitive(buffer);
 		return NULL;
 	}
 
@@ -310,7 +310,7 @@ static void free_dma_buffer(struct vio_dev *vdev, size_t size, void *vaddr,
 	dma_unmap_single(&vdev->dev, dma_handle, size, DMA_BIDIRECTIONAL);
 
 	/* deallocate memory */
-	kzfree(vaddr);
+	kfree_sensitive(vaddr);
 }
 
 /**
@@ -883,7 +883,7 @@ static int ibmvmc_close(struct inode *inode, struct file *file)
 		spin_unlock_irqrestore(&hmc->lock, flags);
 	}
 
-	kzfree(session);
+	kfree_sensitive(session);
 
 	return rc;
 }