Re: [PATCH 4/4] smb/server: add ksmbd_vfs_kern_path()

[Namjae Jeon]

On Thu, Jul 24, 2025 at 8:04 AM NeilBrown <neil@xxxxxxxxxx> wrote:
>
> On Thu, 24 Jul 2025, Stefan Metzmacher wrote:
> > Hi Neil,
> >
> > for me this reliable generates the following problem, just doing a simple:
> > mount -t cifs -ousername=root,password=test,noperm,vers=3.1.1,mfsymlinks,actimeo=0 //172.31.9.167/test /mnt/test/
> >
> > [ 2213.234061] [   T1972] ==================================================================
> > [ 2213.234607] [   T1972] BUG: KASAN: slab-use-after-free in lookup_noperm_common+0x237/0x2b0
>
> Hi,
>  thanks for testing and reporting.  Sorry about this obvious bug...
>
> I called putname() too early.  The following should fix it.  Please test
> and support.
> Namjae: it would be good to squash this into the offending patch before
> submitting upstream.  Can you do that?  Do you want me to resend the
> whole patch?
You don't need to resend the patch. I will directly update and test it.
Thanks!

>
> Thanks,
> NeilBrown
>
> --- a/fs/smb/server/vfs.c
> +++ b/fs/smb/server/vfs.c
> @@ -53,7 +53,7 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
>                                  struct path *path, bool do_lock)
>  {
>         struct qstr last;
> -       struct filename *filename;
> +       struct filename *filename __free(putname) = NULL;
>         struct path *root_share_path = &share_conf->vfs_path;
>         int err, type;
>         struct dentry *d;
> @@ -72,7 +72,6 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
>         err = vfs_path_parent_lookup(filename, flags,
>                                      path, &last, &type,
>                                      root_share_path);
> -       putname(filename);
>         if (err)
>                 return err;
>
>