On Thu, 21 Nov 2024 03:55:29 +0000, Al Viro wrote:
> > user_path_at()->
> > filename_lookup()->
> > path_lookupat()->
> > lookup_last()->
> > walk_component()->
> > __lookup_slow()->
> > ntfs_lookup()->
> > d_splice_alias()->
> >
> > 2. The subsequent chmod fails, causing the inode to be set to bad.
>
> What's wrong with "return an error"?
make_bad_inode() is executed in attr_set_size() and the error code -ENOENT is returned;
attr_set_size() defined in fs/ntfs3/attrib.c
>
> > 3. During the link operation, d_instantiate() is executed in ntfs_link() to associate the bad inode with the dentry.
>
> Yecchhh... If nothing else, check for is_bad_inode() should be there
> for as long as make_bad_inode() is done on live inodes.
I checked is_bad_inode() in ntfs_link(), see line 146 of ntfs_link(), please see my V3 of the patch [2].
[1]
fs/ntfs3/namei.c
19 static int ntfs_link(struct dentry *ode, struct inode *dir, struct dentry *de)
18 {
17 int err;
16 struct inode *inode = d_inode(ode);
15 struct ntfs_inode *ni = ntfs_i(inode);
14
13 if (S_ISDIR(inode->i_mode))
12 return -EPERM;
11
10 if (inode->i_nlink >= NTFS_LINK_MAX)
9 return -EMLINK;
8
7 ni_lock_dir(ntfs_i(dir));
6 if (inode != dir)
5 ni_lock(ni);
4
3 inc_nlink(inode);
2 ihold(inode);
1
146 err = ntfs_link_inode(inode, de);
1
2 if (!err) {
3 inode_set_ctime_current(inode);
4 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
5 mark_inode_dirty(inode);
6 mark_inode_dirty(dir);
7 d_instantiate(de, inode);
[2]
Reported-by: syzbot+73d8fc29ec7cba8286fa@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=73d8fc29ec7cba8286fa
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
V1 --> V2: add the root cause of the i_link not set issue and imporve the check
V2 --> V3: when creating a symbolic link, first check whether the inode of file is bad.
fs/ntfs3/inode.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
index be04d2845bb7..fefbdcf75016 100644
--- a/fs/ntfs3/inode.c
+++ b/fs/ntfs3/inode.c
@@ -1719,6 +1719,9 @@ int ntfs_link_inode(struct inode *inode, struct dentry *dentry)
struct ntfs_sb_info *sbi = inode->i_sb->s_fs_info;
struct NTFS_DE *de;
+ if (is_bad_inode(inode))
+ return -EIO;
+
/* Allocate PATH_MAX bytes. */
de = __getname();
if (!de)
