[PATCH] ntfs: fix missing kstrdup() error check in ntfs_write_volume_label()

[Zhan Xusheng]

ntfs_write_volume_label() does not check the return value of
kstrdup().  If the allocation fails, vol->volume_label is set to
NULL while the function returns success.  A subsequent
FS_IOC_GETFSLABEL then returns an empty string even though the
on-disk label was updated correctly.

Fix by allocating the new label before freeing the old one and
propagating -ENOMEM on failure.  Also move mark_inode_dirty_sync()
into the success path so that it is not called when no metadata was
actually modified.

Fixes: 6251f0b0de7d ("ntfs: update super block operations")
Signed-off-by: Zhan Xusheng <zhanxusheng@xxxxxxxxxx>
---
 fs/ntfs/super.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index 22dc7865eca7..629fac580f95 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -425,7 +425,7 @@ int ntfs_write_volume_label(struct ntfs_volume *vol, char *label)
 		return uname_len;
 	}
 
-	if (uname_len  > NTFS_MAX_LABEL_LEN) {
+	if (uname_len > NTFS_MAX_LABEL_LEN) {
 		ntfs_error(vol->sb,
 			   "Volume label is too long (max %d characters).",
 			   NTFS_MAX_LABEL_LEN);
@@ -437,7 +437,7 @@ int ntfs_write_volume_label(struct ntfs_volume *vol, char *label)
 	ctx = ntfs_attr_get_search_ctx(vol_ni, NULL);
 	if (!ctx) {
 		ret = -ENOMEM;
-		goto  out;
+		goto out;
 	}
 
 	if (!ntfs_attr_lookup(AT_VOLUME_NAME, NULL, 0, 0, 0, NULL, 0,
@@ -450,11 +450,15 @@ int ntfs_write_volume_label(struct ntfs_volume *vol, char *label)
 out:
 	mutex_unlock(&vol_ni->mrec_lock);
 	kvfree(uname);
-	mark_inode_dirty_sync(vol->vol_ino);
 
 	if (ret >= 0) {
+		char *new_label = kstrdup(label, GFP_KERNEL);
+
+		if (!new_label)
+			return -ENOMEM;
 		kfree(vol->volume_label);
-		vol->volume_label = kstrdup(label, GFP_KERNEL);
+		vol->volume_label = new_label;
+		mark_inode_dirty_sync(vol->vol_ino);
 		ret = 0;
 	}
 	return ret;
-- 
2.43.0