eCryptfs: Fix metadata in xattr feature regression

Fixes regression in 8faece5f

When using the ecryptfs_xattr_metadata mount option, eCryptfs stores the
metadata (normally stored at the front of the file) in the user.ecryptfs
xattr.  This causes ecryptfs_crypt_stat.num_header_bytes_at_front to be
0, since there is no header data at the front of the file.  This results
in too much memory being requested and ENOMEM being returned from
ecryptfs_write_metadata().

This patch fixes the problem by using the num_header_bytes_at_front
variable for specifying the max size of the metadata, despite whether it
is stored in the header or xattr.
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/crypto.c

@@ -381,8 +381,8 @@ static int encrypt_scatterlist(struct ecryptfs_crypt_stat *crypt_stat,
 static void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
 					     struct ecryptfs_crypt_stat *crypt_stat)
 {
-	(*offset) = (crypt_stat->num_header_bytes_at_front
-		     + (crypt_stat->extent_size * extent_num));
+	(*offset) = ecryptfs_lower_header_size(crypt_stat)
+		    + (crypt_stat->extent_size * extent_num);
 }
 
 /**
@@ -834,7 +834,8 @@ void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
 	set_extent_mask_and_shift(crypt_stat);
 	crypt_stat->iv_bytes = ECRYPTFS_DEFAULT_IV_BYTES;
 	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
-		crypt_stat->num_header_bytes_at_front = 0;
+		crypt_stat->num_header_bytes_at_front =
+					ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
 	else {
 		if (PAGE_CACHE_SIZE <= ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)
 			crypt_stat->num_header_bytes_at_front =

fs/ecryptfs/ecryptfs_kernel.h

@@ -464,6 +464,14 @@ struct ecryptfs_daemon {
 
 extern struct mutex ecryptfs_daemon_hash_mux;
 
+static inline size_t
+ecryptfs_lower_header_size(struct ecryptfs_crypt_stat *crypt_stat)
+{
+	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
+		return 0;
+	return crypt_stat->num_header_bytes_at_front;
+}
+
 static inline struct ecryptfs_file_info *
 ecryptfs_file_to_private(struct file *file)
 {

fs/ecryptfs/inode.c

@@ -768,7 +768,7 @@ upper_size_to_lower_size(struct ecryptfs_crypt_stat *crypt_stat,
 {
 	loff_t lower_size;
 
-	lower_size = crypt_stat->num_header_bytes_at_front;
+	lower_size = ecryptfs_lower_header_size(crypt_stat);
 	if (upper_size != 0) {
 		loff_t num_extents;
 

fs/ecryptfs/mmap.c

@@ -97,19 +97,6 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  *                        (big-endian)
  *     Octet  26:         Begin RFC 2440 authentication token packet set
  */
-static void set_header_info(char *page_virt,
-			    struct ecryptfs_crypt_stat *crypt_stat)
-{
-	size_t written;
-	size_t save_num_header_bytes_at_front =
-		crypt_stat->num_header_bytes_at_front;
-
-	crypt_stat->num_header_bytes_at_front =
-		ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
-	ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
-	crypt_stat->num_header_bytes_at_front =
-		save_num_header_bytes_at_front;
-}
 
 /**
  * ecryptfs_copy_up_encrypted_with_header
@@ -146,9 +133,13 @@ ecryptfs_copy_up_encrypted_with_header(struct page *page,
 			memset(page_virt, 0, PAGE_CACHE_SIZE);
 			/* TODO: Support more than one header extent */
 			if (view_extent_num == 0) {
+				size_t written;
+
 				rc = ecryptfs_read_xattr_region(
 					page_virt, page->mapping->host);
-				set_header_info(page_virt, crypt_stat);
+				ecryptfs_write_header_metadata(page_virt + 20,
+							       crypt_stat,
+							       &written);
 			}
 			kunmap_atomic(page_virt, KM_USER0);
 			flush_dcache_page(page);