linux-kernel - Re: [PATCH 4/4] smb/server: add ksmbd_vfs_kern

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Message-ID: <CAKYAXd_0kqhD9mYNxO_m8NzN4N=s2ReMrMNJxys89DQ_1uo+fQ@mail.gmail.com>
Date: Thu, 24 Jul 2025 08:19:49 +0900
From: Namjae Jeon <linkinjeon@...nel.org>
To: NeilBrown <neil@...wn.name>
Cc: Stefan Metzmacher <metze@...ba.org>, Steve French <smfrench@...il.com>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, Tom Talpey <tom@...pey.com>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	linux-fsdevel@...r.kernel.org, linux-cifs@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] smb/server: add ksmbd_vfs_kern_path()

On Thu, Jul 24, 2025 at 8:04 AM NeilBrown <neil@...wn.name> 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;
>
>