linux-kernel - [PATCH 5/6] ubifs: do_rename: Fix wrong space budget when target inode's nlink

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Date:   Tue, 11 Oct 2022 11:47:31 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <richard@....at>, <s.hauer@...gutronix.de>,
        <miquel.raynal@...tlin.com>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <chengzhihao1@...wei.com>, <yukuai3@...wei.com>
Subject: [PATCH 5/6] ubifs: do_rename: Fix wrong space budget when target inode's nlink > 1

If target inode is a special file (eg. block/char device) with nlink
count greater than 1, the inode with ui->data will be re-written on
disk. However, UBIFS losts target inode's data_len while doing space
budget. Bad space budget may let make_reservation() return with -ENOSPC,
which could turn ubifs to read-only mode in do_writepage() process.

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216494
Fixes: 1e51764a3c2ac0 ("UBIFS: add new flash file system")
Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
---
 fs/ubifs/dir.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 53c5442f48b7..a77e859246c3 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -1323,6 +1323,8 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (unlink) {
 		ubifs_assert(c, inode_is_locked(new_inode));
 
+		/* Budget for old inode's data when its nlink > 1. */
+		req.dirtied_ino_d = ALIGN(ubifs_inode(new_inode)->data_len, 8);
 		err = ubifs_purge_xattrs(new_inode);
 		if (err)
 			return err;
-- 
2.31.1