[PATCH 5.10 019/122] fuse: check if copy_file_range() returns larger than requested size

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@redhat.com>

commit e5203209b3935041dac541bc5b37efb44220cc0b upstream.

Just like write(), copy_file_range() should check if the return value is
less or equal to the requested number of bytes.

Reported-by: Chunsheng Luo <luochunsheng@ustc.edu>
Closes: https://lore.kernel.org/all/20250807062425.694-1-luochunsheng@ustc.edu/
Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()")
Cc: <stable@vger.kernel.org> # v4.20
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/fuse/file.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3450,6 +3450,9 @@ static ssize_t __fuse_copy_file_range(st
 		fc->no_copy_file_range = 1;
 		err = -EOPNOTSUPP;
 	}
+	if (!err && outarg.size > len)
+		err = -EIO;
+
 	if (err)
 		goto out;