[PATCH AUTOSEL 6.12 09/36] udf: Verify inode link counts before performing rename

[Sasha Levin <sashal@kernel.org>]

From: Jan Kara <jack@suse.cz>

[ Upstream commit 6756af923e06aa33ad8894aaecbf9060953ba00f ]

During rename, we are updating link counts of various inodes either when
rename deletes target or when moving directory across directories.
Verify involved link counts are sane so that we don't trip warnings in
VFS.

Reported-by: syzbot+3ff7365dc04a6bcafa66@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/udf/namei.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 2be775d30ac10..2cb49b6b07168 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -791,8 +791,18 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 			retval = -ENOTEMPTY;
 			if (!empty_dir(new_inode))
 				goto out_oiter;
+			retval = -EFSCORRUPTED;
+			if (new_inode->i_nlink != 2)
+				goto out_oiter;
 		}
+		retval = -EFSCORRUPTED;
+		if (old_dir->i_nlink < 3)
+			goto out_oiter;
 		is_dir = true;
+	} else if (new_inode) {
+		retval = -EFSCORRUPTED;
+		if (new_inode->i_nlink < 1)
+			goto out_oiter;
 	}
 	if (is_dir && old_dir != new_dir) {
 		retval = udf_fiiter_find_entry(old_inode, &dotdot_name,
-- 
2.43.0