eCryptfs: Cleanup and optimize ecryptfs_lookup_interpose()

ecryptfs_lookup_interpose() has turned into spaghetti code over the
years. This is an effort to clean it up.

 - Shorten overly descriptive variable names such as ecryptfs_dentry
 - Simplify gotos and error paths
 - Create helper function for reading plaintext i_size from metadata

It also includes an optimization when reading i_size from the metadata.
A complete page-sized kmem_cache_alloc() was being done to read in 16
bytes of metadata. The buffer for that is now statically declared.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

3 files changed, 88 insertions, 105 deletions

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 162f9ba..66d8e67 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1201,24 +1201,19 @@ int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
 	return rc;
 }
 
-int ecryptfs_read_and_validate_header_region(char *data,
-					     struct inode *ecryptfs_inode)
+int ecryptfs_read_and_validate_header_region(struct inode *inode)
 {
-	struct ecryptfs_crypt_stat *crypt_stat =
-		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
+	u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
+	u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
 	int rc;
 
-	if (crypt_stat->extent_size == 0)
-		crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
-	rc = ecryptfs_read_lower(data, 0, crypt_stat->extent_size,
-				 ecryptfs_inode);
-	if (rc < 0) {
-		printk(KERN_ERR "%s: Error reading header region; rc = [%d]\n",
-		       __func__, rc);
-		goto out;
-	}
-	rc = ecryptfs_validate_marker(data + ECRYPTFS_FILE_SIZE_BYTES);
-out:
+	rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
+				 inode);
+	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
+		return rc >= 0 ? -EINVAL : rc;
+	rc = ecryptfs_validate_marker(marker);
+	if (!rc)
+		ecryptfs_i_size_init(file_size, inode);
 	return rc;
 }
 
@@ -1562,19 +1557,21 @@ out:
 	return rc;
 }
 
-int ecryptfs_read_and_validate_xattr_region(char *page_virt,
+int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
 					    struct inode *inode)
 {
+	u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
+	u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
 	int rc;
 
-	rc = ecryptfs_read_xattr_region(page_virt, inode);
-	if (rc)
-		goto out;
-	rc = ecryptfs_validate_marker(page_virt + ECRYPTFS_FILE_SIZE_BYTES);
-	if (rc)
-		printk(KERN_WARNING "Valid data found in [%s] xattr, but "
-			"the marker is invalid\n", ECRYPTFS_XATTR_NAME);
-out:
+	rc = ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
+				     ECRYPTFS_XATTR_NAME, file_size,
+				     ECRYPTFS_SIZE_AND_MARKER_BYTES);
+	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
+		return rc >= 0 ? -EINVAL : rc;
+	rc = ecryptfs_validate_marker(marker);
+	if (!rc)
+		ecryptfs_i_size_init(file_size, inode);
 	return rc;
 }
 
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 72aa24a..8297dda 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -200,6 +200,8 @@ ecryptfs_get_key_payload_data(struct key *key)
 #define MAGIC_ECRYPTFS_MARKER 0x3c81b7f5
 #define MAGIC_ECRYPTFS_MARKER_SIZE_BYTES 8	/* 4*2 */
 #define ECRYPTFS_FILE_SIZE_BYTES (sizeof(u64))
+#define ECRYPTFS_SIZE_AND_MARKER_BYTES (ECRYPTFS_FILE_SIZE_BYTES \
+					+ MAGIC_ECRYPTFS_MARKER_SIZE_BYTES)
 #define ECRYPTFS_DEFAULT_CIPHER "aes"
 #define ECRYPTFS_DEFAULT_KEY_BYTES 16
 #define ECRYPTFS_DEFAULT_HASH "md5"
@@ -659,9 +661,8 @@ int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry);
 void ecryptfs_write_crypt_stat_flags(char *page_virt,
 				     struct ecryptfs_crypt_stat *crypt_stat,
 				     size_t *written);
-int ecryptfs_read_and_validate_header_region(char *data,
-					     struct inode *ecryptfs_inode);
-int ecryptfs_read_and_validate_xattr_region(char *page_virt,
+int ecryptfs_read_and_validate_header_region(struct inode *inode);
+int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
 					    struct inode *inode);
 u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes);
 int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code);
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index f0ad965..7349ade 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -307,105 +307,90 @@ out:
 	return rc;
 }
 
+static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
+{
+	struct ecryptfs_crypt_stat *crypt_stat;
+	int rc;
+
+	rc = ecryptfs_get_lower_file(dentry, inode);
+	if (rc) {
+		printk(KERN_ERR "%s: Error attempting to initialize "
+			"the lower file for the dentry with name "
+			"[%s]; rc = [%d]\n", __func__,
+			dentry->d_name.name, rc);
+		return rc;
+	}
+
+	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
+	/* TODO: lock for crypt_stat comparison */
+	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
+		ecryptfs_set_default_sizes(crypt_stat);
+
+	rc = ecryptfs_read_and_validate_header_region(inode);
+	ecryptfs_put_lower_file(inode);
+	if (rc) {
+		rc = ecryptfs_read_and_validate_xattr_region(dentry, inode);
+		if (!rc)
+			crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
+	}
+
+	/* Must return 0 to allow non-eCryptfs files to be looked up, too */
+	return 0;
+}
+
 /**
  * ecryptfs_lookup_interpose - Dentry interposition for a lookup
  */
-static int ecryptfs_lookup_interpose(struct dentry *ecryptfs_dentry,
+static int ecryptfs_lookup_interpose(struct dentry *dentry,
 				     struct dentry *lower_dentry,
-				     struct inode *ecryptfs_dir_inode)
+				     struct inode *dir_inode)
 {
-	struct dentry *lower_dir_dentry;
+	struct inode *inode, *lower_inode = lower_dentry->d_inode;
+	struct ecryptfs_dentry_info *dentry_info;
 	struct vfsmount *lower_mnt;
-	struct inode *inode, *lower_inode;
-	struct ecryptfs_crypt_stat *crypt_stat;
-	char *page_virt = NULL;
-	int put_lower = 0, rc = 0;
-
-	lower_dir_dentry = lower_dentry->d_parent;
-	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(
-				   ecryptfs_dentry->d_parent));
-	lower_inode = lower_dentry->d_inode;
-	fsstack_copy_attr_atime(ecryptfs_dir_inode, lower_dir_dentry->d_inode);
+	int rc = 0;
+
+	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
+	fsstack_copy_attr_atime(dir_inode, lower_dentry->d_parent->d_inode);
 	BUG_ON(!lower_dentry->d_count);
-	ecryptfs_set_dentry_private(ecryptfs_dentry,
-				    kmem_cache_alloc(ecryptfs_dentry_info_cache,
-						     GFP_KERNEL));
-	if (!ecryptfs_dentry_to_private(ecryptfs_dentry)) {
-		rc = -ENOMEM;
+
+	dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
+	ecryptfs_set_dentry_private(dentry, dentry_info);
+	if (!dentry_info) {
 		printk(KERN_ERR "%s: Out of memory whilst attempting "
 		       "to allocate ecryptfs_dentry_info struct\n",
 			__func__);
-		goto out_put;
+		dput(lower_dentry);
+		mntput(lower_mnt);
+		d_drop(dentry);
+		return -ENOMEM;
 	}
-	ecryptfs_set_dentry_lower(ecryptfs_dentry, lower_dentry);
-	ecryptfs_set_dentry_lower_mnt(ecryptfs_dentry, lower_mnt);
+	ecryptfs_set_dentry_lower(dentry, lower_dentry);
+	ecryptfs_set_dentry_lower_mnt(dentry, lower_mnt);
+
 	if (!lower_dentry->d_inode) {
 		/* We want to add because we couldn't find in lower */
-		d_add(ecryptfs_dentry, NULL);
-		goto out;
+		d_add(dentry, NULL);
+		return 0;
 	}
-	inode = __ecryptfs_get_inode(lower_inode, ecryptfs_dir_inode->i_sb);
+	inode = __ecryptfs_get_inode(lower_inode, dir_inode->i_sb);
 	if (IS_ERR(inode)) {
-		rc = PTR_ERR(inode);
-		printk(KERN_ERR "%s: Error interposing; rc = [%d]\n",
-		       __func__, rc);
-		goto out;
-	}
-	if (!S_ISREG(inode->i_mode)) {
-		if (inode->i_state & I_NEW)
-			unlock_new_inode(inode);
-		d_add(ecryptfs_dentry, inode);
-		goto out;
-	}
-	/* Released in this function */
-	page_virt = kmem_cache_zalloc(ecryptfs_header_cache_2, GFP_USER);
-	if (!page_virt) {
-		printk(KERN_ERR "%s: Cannot kmem_cache_zalloc() a page\n",
-		       __func__);
-		rc = -ENOMEM;
-		make_bad_inode(inode);
-		goto out;
-	}
-	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
-	if (rc) {
-		printk(KERN_ERR "%s: Error attempting to initialize "
-			"the lower file for the dentry with name "
-			"[%s]; rc = [%d]\n", __func__,
-			ecryptfs_dentry->d_name.name, rc);
-		make_bad_inode(inode);
-		goto out_free_kmem;
+		printk(KERN_ERR "%s: Error interposing; rc = [%ld]\n",
+		       __func__, PTR_ERR(inode));
+		return PTR_ERR(inode);
 	}
-	put_lower = 1;
-	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
-	/* TODO: lock for crypt_stat comparison */
-	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
-			ecryptfs_set_default_sizes(crypt_stat);
-	rc = ecryptfs_read_and_validate_header_region(page_virt, inode);
-	if (rc) {
-		memset(page_virt, 0, PAGE_CACHE_SIZE);
-		rc = ecryptfs_read_and_validate_xattr_region(page_virt,
-							     inode);
+	if (S_ISREG(inode->i_mode)) {
+		rc = ecryptfs_i_size_read(dentry, inode);
 		if (rc) {
-			rc = 0;
-			goto unlock_inode;
+			make_bad_inode(inode);
+			return rc;
 		}
-		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 	}
-	ecryptfs_i_size_init(page_virt, inode);
-unlock_inode:
+
 	if (inode->i_state & I_NEW)
 		unlock_new_inode(inode);
-	d_add(ecryptfs_dentry, inode);
-out_free_kmem:
-	kmem_cache_free(ecryptfs_header_cache_2, page_virt);
-	goto out;
-out_put:
-	dput(lower_dentry);
-	mntput(lower_mnt);
-	d_drop(ecryptfs_dentry);
-out:
-	if (put_lower)
-		ecryptfs_put_lower_file(inode);
+	d_add(dentry, inode);
+
 	return rc;
 }