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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Wed, 19 May 2021 06:03:41 +0200
Message-ID: <CAJfpegv_TPLFumONsoCOKP5vuO7Gdy91TkV3LUvNg4tdPSs6zA@mail.gmail.com>
Subject: Re: [PATCH] ovl: useing ovl_revert_creds() instead of revert_creds(),
To:     Yao Haidong <yaohaidong369@gmail.com>
Cc:     Orson Zhai <orsonzhai@gmail.com>,
        Chunyan Zhang <zhang.lyra@gmail.com>,
        Chunyan Zhang <Chunyan.Zhang@unisoc.com>,
        Orson Zhai <Orson.Zhai@unisoc.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        network dev <netdev@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, stable <stable@vger.kernel.org>,
        Haidong Yao <haidong.yao@unisoc.com>
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On Wed, 19 May 2021 at 05:29, Yao Haidong <yaohaidong369@gmail.com> wrote:

> Miklos Szeredi <miklos@szeredi.hu> =E4=BA=8E2021=E5=B9=B45=E6=9C=8818=E6=
=97=A5=E5=91=A8=E4=BA=8C =E4=B8=8B=E5=8D=889:41=E5=86=99=E9=81=93=EF=BC=9A
> >
> > On Tue, 18 May 2021 at 14:21, Haidong Yao <yaohaidong369@gmail.com> wro=
te:
> > >
> > > From: Haidong Yao <haidong.yao@unisoc.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 =3D 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=EF=BC=8Cold_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