netdev - Re: [PATCH 1/3] bpf: Don't check for current being NULL

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Message-ID: <20171016223105.c3ww4nf5kvrseebh@ast-mbp.dhcp.thefacebook.com>
Date:   Mon, 16 Oct 2017 15:31:07 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Richard Weinberger <richard@....at>
Cc:     Al Viro <viro@....linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>, linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/3] bpf: Don't check for current being NULL

On Tue, Oct 17, 2017 at 12:23:13AM +0200, Richard Weinberger wrote:
> Alexei,
> 
> Am Dienstag, 17. Oktober 2017, 00:06:08 CEST schrieb Alexei Starovoitov:
> > On Mon, Oct 16, 2017 at 11:18 AM, Richard Weinberger <richard@....at> wrote:
> > > current is never NULL.
> > > 
> > > Signed-off-by: Richard Weinberger <richard@....at>
> > > ---
> > > 
> > >  kernel/bpf/helpers.c | 12 ------------
> > >  1 file changed, 12 deletions(-)
> > > 
> > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > > index 3d24e238221e..e8845adcd15e 100644
> > > --- a/kernel/bpf/helpers.c
> > > +++ b/kernel/bpf/helpers.c
> > > @@ -120,9 +120,6 @@ BPF_CALL_0(bpf_get_current_pid_tgid)
> > > 
> > >  {
> > >  
> > >         struct task_struct *task = current;
> > > 
> > > -       if (unlikely(!task))
> > > -               return -EINVAL;
> > > -
> > 
> > really? in all context? including irq and nmi?
> 
> I would be astonished current is NULL in such a context.
> 
> To be sure, let's CC linux-arch.
> IIRC I talked also with Al about this and he also assumed that current
> cannot be NULL.

Hmm I probably mistakenly stole the !current check from somewhere.
Happy to delete all these checks then.