[PATCH 3/7] ecryptfs: use kzalloc() for the header buffer

[Tal Zussman]

ecryptfs_write_metadata() is only called when a file is created,
where ecryptfs_set_default_sizes() has set metadata_size to
ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE (8 KiB), or PAGE_SIZE if that is
larger. That is an acceptable size for kmalloc(), and the buffer is
only written out with kernel_write() or as an xattr, so it doesn't
need to be page-aligned. Allocate it with kzalloc() and remove
ecryptfs_get_zeroed_pages().

Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
---
 fs/ecryptfs/crypto.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 9b8b0c5a81cd..6a014872e919 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -998,17 +998,6 @@ ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
 	return rc;
 }
 
-static unsigned long ecryptfs_get_zeroed_pages(gfp_t gfp_mask,
-					       unsigned int order)
-{
-	struct page *page;
-
-	page = alloc_pages(gfp_mask | __GFP_ZERO, order);
-	if (page)
-		return (unsigned long) page_address(page);
-	return 0;
-}
-
 /**
  * ecryptfs_write_metadata
  * @ecryptfs_dentry: The eCryptfs dentry, which should be negative
@@ -1027,7 +1016,6 @@ int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
 {
 	struct ecryptfs_crypt_stat *crypt_stat =
 		&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
-	unsigned int order;
 	char *virt;
 	size_t virt_len;
 	size_t size = 0;
@@ -1046,15 +1034,14 @@ int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
 		goto out;
 	}
 	virt_len = crypt_stat->metadata_size;
-	order = get_order(virt_len);
 	/* Released in this function */
-	virt = (char *)ecryptfs_get_zeroed_pages(GFP_KERNEL, order);
+	virt = kzalloc(virt_len, GFP_KERNEL);
 	if (!virt) {
 		printk(KERN_ERR "%s: Out of memory\n", __func__);
 		rc = -ENOMEM;
 		goto out;
 	}
-	/* Zeroed page ensures the in-header unencrypted i_size is set to 0 */
+	/* Zeroed buffer ensures the in-header unencrypted i_size is set to 0 */
 	rc = ecryptfs_write_headers_virt(virt, virt_len, &size, crypt_stat,
 					 ecryptfs_dentry);
 	if (unlikely(rc)) {
@@ -1074,7 +1061,7 @@ int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
 		goto out_free;
 	}
 out_free:
-	free_pages((unsigned long)virt, order);
+	kfree(virt);
 out:
 	return rc;
 }

-- 
2.39.5