[PATCH 1/3] xfs: Do not unshare ranges beyond EOF

[Julian Sun <sunjunchao2870@gmail.com>]

Attempting to unshare extents beyond EOF will trigger
the need zeroing case, which in turn triggers a warning.
Therefore, let's skip the unshare process if extents are
beyond EOF.

Reported-and-tested-by: syzbot+296b1c84b9cbf306e5a0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=296b1c84b9cbf306e5a0
Fixes: 32a38a499104 ("iomap: use write_begin to read pages to unshare")
Inspired-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Julian Sun <sunjunchao2870@gmail.com>
---
 fs/xfs/xfs_reflink.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 6fde6ec8092f..65509ff6aba0 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2016 Oracle.  All Rights Reserved.
  * Author: Darrick J. Wong <darrick.wong@oracle.com>
  */
+#include "linux/fs.h"
 #include "xfs.h"
 #include "xfs_fs.h"
 #include "xfs_shared.h"
@@ -1669,6 +1670,9 @@ xfs_reflink_unshare(
 
 	if (!xfs_is_reflink_inode(ip))
 		return 0;
+	/* don't try to unshare any ranges beyond EOF. */
+	if (offset + len > i_size_read(inode))
+		len = i_size_read(inode) - offset;
 
 	trace_xfs_reflink_unshare(ip, offset, len);
 
-- 
2.39.2