[PATCH] ntfs: fix error handling in ntfs_readdir()

[Hongling Zeng]

ntfs_readdir() converts all non-zero errors to success before returning.
This hides real errors such as -ENOMEM or -EIO from userspace and makes
them look like end-of-directory.

Only positive return values from ntfs_filldir(), which indicate that the
user buffer is full, should be converted to 0. Negative errors should be
propagated.

Additionally, when the user buffer is full (err > 0), the iterator should
not be marked as completed since directory traversal has not ended.
This allows subsequent readdir() calls to continue from the saved position.

Fixes: 956ce2083c93 ("[readdir] convert ntfs")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hongling Zeng <zenghongling@xxxxxxxxxx>
---
 fs/ntfs/dir.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/ntfs/dir.c b/fs/ntfs/dir.c
index 2d594cbb4ebe..ba17d9805326 100644
--- a/fs/ntfs/dir.c
+++ b/fs/ntfs/dir.c
@@ -982,8 +982,10 @@ static int ntfs_readdir(struct file *file, struct dir_context *actor)
 
 	if (!err)
 		private->end_in_iterate = true;
-	else
+	else if (err > 0)
 		err = 0;
+	else
+		goto out;
 
 	private->curr_pos = actor->pos = ie_pos;
 out:
@@ -1000,12 +1002,13 @@ static int ntfs_readdir(struct file *file, struct dir_context *actor)
 		kfree(cnir);
 	}
 
-	if (err) {
+	if (err > 0) {
 		if (private) {
 			private->curr_pos = actor->pos;
-			private->end_in_iterate = true;
 		}
 		err = 0;
+	} else if (err < 0 && private) {
+		private->curr_pos = actor->pos;
 	}
 	ntfs_index_ctx_put(ictx);
 	kfree(name);
-- 
2.25.1