[PATCH v4 24/31] ntfs: serialize and report export parent reconstruction errors

[Baolin Liu]

From: Xuewen Wang <wangxuewen@xxxxxxxxxx>

Exportfs calls ntfs_get_parent() without the child inode lock. Hold the
child's mrec_lock across FILE_NAME lookup and parent loading to stabilize
corruption checks against rename and rmdir.

Report an unused parent as EFSCORRUPTED only for a linked, non-deleting
child. Report missing required or malformed FILE_NAME attributes, while
continuing past malformed candidates as before. Release the lock before
d_obtain_alias().

Preserve ordinary stale-handle behavior. NTFS returns EFSCORRUPTED for a
confirmed corrupt parent reference; generic open_by_handle_at() decoding
still converts that error to ESTALE.

Signed-off-by: Xuewen Wang <wangxuewen@xxxxxxxxxx>
---
 fs/ntfs/namei.c | 43 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 9 deletions(-)

diff --git a/fs/ntfs/namei.c b/fs/ntfs/namei.c
index 47e52270e8ee..a64ab7881052 100644
--- a/fs/ntfs/namei.c
+++ b/fs/ntfs/namei.c
@@ -1730,7 +1730,8 @@ const struct inode_operations ntfs_dir_inode_ops = {
  * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
  * default ->decode_fh() which is export_decode_fh() in the same file.
  *
- * Note: ntfs_get_parent() is called with @d_inode(child_dent)->i_mutex down.
+ * Serialize the file name lookup and parent load against rename and rmdir
+ * with the child's mrec_lock; exportfs does not hold the child's inode lock.
  *
  * Return the dentry of the parent directory on success or the error code on
  * error (IS_ERR() is true).
@@ -1738,6 +1739,7 @@ const struct inode_operations ntfs_dir_inode_ops = {
 static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 {
 	struct inode *vi = d_inode(child_dent);
+	struct inode *parent;
 	struct ntfs_inode *ni = NTFS_I(vi);
 	struct mft_record *mrec;
 	struct ntfs_attr_search_ctx *ctx;
@@ -1747,15 +1749,20 @@ static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 	int err;
 
 	ntfs_debug("Entering for inode 0x%llx.", ni->mft_no);
+	mutex_lock(&ni->mrec_lock);
 	/* Get the mft record of the inode belonging to the child dentry. */
 	mrec = map_mft_record(ni);
-	if (IS_ERR(mrec))
-		return ERR_CAST(mrec);
+	if (IS_ERR(mrec)) {
+		err = PTR_ERR(mrec);
+		goto unlock_err;
+	}
 	/* Find the first file name attribute in the mft record. */
 	ctx = ntfs_attr_get_search_ctx(ni, mrec);
 	if (IS_ERR(ctx)) {
 		unmap_mft_record(ni);
-		return ERR_PTR(PTR_ERR(ctx));
+		err = PTR_ERR(ctx);
+		ctx = NULL;
+		goto unlock_err;
 	}
 try_next:
 	err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
@@ -1763,27 +1770,45 @@ static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 	if (unlikely(err)) {
 		ntfs_attr_put_search_ctx(ctx);
 		unmap_mft_record(ni);
-		if (err == -ENOENT)
+		if (err == -ENOENT && vi->i_nlink) {
+			err = -EFSCORRUPTED;
+			ntfs_report_file_metadata_error(vi, -EFSCORRUPTED);
 			ntfs_error(vi->i_sb,
 				   "Inode 0x%llx does not have a file name attribute.  Run chkdsk.",
 				   ni->mft_no);
-		return ERR_PTR(err);
+		}
+		goto unlock_err;
 	}
 	attr = ctx->attr;
-	if (unlikely(attr->non_resident))
+	if (unlikely(attr->non_resident)) {
+		ntfs_report_file_metadata_error(vi, -EFSCORRUPTED);
 		goto try_next;
+	}
 	fn = (struct file_name_attr *)((u8 *)attr +
 			le16_to_cpu(attr->data.resident.value_offset));
 	if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
-	    (u8 *)attr + le32_to_cpu(attr->length)))
+	    (u8 *)attr + le32_to_cpu(attr->length))) {
+		ntfs_report_file_metadata_error(vi, -EFSCORRUPTED);
 		goto try_next;
+	}
 	/* Get the inode number of the parent directory. */
 	parent_ino = MREF_LE(fn->parent_directory);
 	/* Release the search context and the mft record of the child. */
 	ntfs_attr_put_search_ctx(ctx);
 	unmap_mft_record(ni);
 
-	return d_obtain_alias(ntfs_iget(vi->i_sb, parent_ino));
+	parent = ntfs_iget(vi->i_sb, parent_ino);
+	if (IS_ERR(parent) && PTR_ERR(parent) == -ENOENT &&
+	    vi->i_nlink && !NInoBeingDeleted(ni)) {
+		ntfs_report_file_metadata_error(vi, -EFSCORRUPTED);
+		parent = ERR_PTR(-EFSCORRUPTED);
+	}
+	mutex_unlock(&ni->mrec_lock);
+	return d_obtain_alias(parent);
+
+unlock_err:
+	mutex_unlock(&ni->mrec_lock);
+	return ERR_PTR(err);
 }
 
 static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
-- 
2.51.0