netdev - Re: [PATCH] ovl: useing ovl_revert_creds() instead of revert

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Date:   Wed, 19 May 2021 06:03:41 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Yao Haidong <yaohaidong369@...il.com>
Cc:     Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Chunyan Zhang <Chunyan.Zhang@...soc.com>,
        Orson Zhai <Orson.Zhai@...soc.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        overlayfs <linux-unionfs@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        network dev <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, stable <stable@...r.kernel.org>,
        Haidong Yao <haidong.yao@...soc.com>
Subject: Re: [PATCH] ovl: useing ovl_revert_creds() instead of revert_creds(),

On Wed, 19 May 2021 at 05:29, Yao Haidong <yaohaidong369@...il.com> wrote:

> Miklos Szeredi <miklos@...redi.hu> 于2021年5月18日周二 下午9:41写道：
> >
> > On Tue, 18 May 2021 at 14:21, Haidong Yao <yaohaidong369@...il.com> wrote:
> > >
> > > From: Haidong Yao <haidong.yao@...soc.com>

[...]

> > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> > > index 4d53d3b7e5fe..d9bc658f22ee 100644
> > > --- a/fs/overlayfs/file.c
> > > +++ b/fs/overlayfs/file.c
> > > @@ -60,7 +60,7 @@ static struct file *ovl_open_realfile(const struct file *file,
> > >                 realfile = open_with_fake_path(&file->f_path, flags, realinode,
> > >                                                current_cred());
> > >         }
> > > -       revert_creds(old_cred);
> > > +       ovl_revert_creds(inode->i_sb, old_cred);
> >
> > Upstream kernel doesn't have ovl_revert_creds().

> Hi Miklos:
>
> Sorry,
> Sometimes，old_cred is NULL.
> Do you think this is a problem?
> Can I add ovl_revert_creds()? or You have a better way?

old_cred can't be NULL on upstream (Linus) kernel.

>From the taint flags I can see that this is some weird setup.  Please
contact the distro that is providing the kerne/modules about this
issue.  It's not anything the upstream kernel maintainers can help
with.

Thanks,
Miklos