[PATCH 2/2] fs/ntfs3: don't mark pages uptodate when ni_read_frame() fails

[Senjin <senjin@hatchling.org>]

ni_read_frame() calls SetPageUptodate() on every page of the frame on
exit, including when reading or decompressing the frame failed. The
pages then hold zeroes or partially decompressed data, and that is
served as valid file data until the page cache is dropped.

The error is also lost for the folio that was actually requested:
ni_read_folio_cmpr() returns it from ->read_folio, but
filemap_read_folio() only checks folio_test_uptodate() afterwards and
treats the read as successful. Userspace gets wrong data, read() returns
no error, and nothing is logged.

Only mark the pages uptodate when the frame was read successfully. On
failure the requested folio is left !uptodate and the read returns an
error; the other pages of the frame are retried on their next access.

With the bug fixed by the previous patch still present, a read of an
affected file now fails with an error after the last good frame, instead
of silently returning zeroes.

Fixes: f35590ee26f5 ("fs/ntfs3: remove ntfs_bio_pages and use page cache for compressed I/O")
Cc: stable@vger.kernel.org # 6.19+
Signed-off-by: Senjin <senjin@hatchling.org>
---
 fs/ntfs3/frecord.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index bead01a..a8b696d 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -2287,7 +2287,6 @@ int ni_read_frame(struct ntfs_inode *ni, u64 frame_vbo, struct page **pages,
 	u64 vbo_disk;
 	size_t unc_size = 0;
 	u32 frame_size, i, ondisk_size;
-	struct page *pg;
 	struct ATTRIB *attr;
 	CLST frame, clst_data;
 
@@ -2519,9 +2518,14 @@ out1:
 #endif
 	vunmap(frame_mem);
 out:
-	for (i = 0; i < pages_per_frame; i++) {
-		pg = pages[i];
-		SetPageUptodate(pg);
+	/*
+	 * Only mark the pages uptodate if the frame was read successfully,
+	 * otherwise zeroed or partially decompressed pages would be served
+	 * from the page cache as valid data.
+	 */
+	if (!err) {
+		for (i = 0; i < pages_per_frame; i++)
+			SetPageUptodate(pages[i]);
 	}
 
 	return err;
-- 
2.56.0