[PATCH] fs/ntfs3: Fix integer overflow in ni_fiemap with fiemap_prep()

[Kari Argillander]

Use fiemap_prep() to check valid flags. It also shrink request scope
(@len) to what the fs can actually handle.

This address following Smatch static checker warning:
	fs/ntfs3/frecord.c:1894 ni_fiemap()
	warn: potential integer overflow from user 'vbo + len'

Because fiemap_prep() shrinks @len this cannot happened anymore.

Reported-by Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: lore.kernel.org/ntfs3/20210825080440.GA17407@kili/

Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Signed-off-by: Kari Argillander <kari.argillander@xxxxxxxxx>
---
 fs/ntfs3/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 59344985c2e8..cb736701f2cc 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -1210,8 +1210,9 @@ int ntfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	int err;
 	struct ntfs_inode *ni = ntfs_i(inode);
 
-	if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR)
-		return -EOPNOTSUPP;
+	err = fiemap_prep(inode, fieinfo, start, &len, ~FIEMAP_FLAG_XATTR);
+	if (err)
+		return err;
 
 	ni_lock(ni);
 
-- 
2.30.2