netdev - Re: [PATCH 8/9] bpf: Check address length before reading address family

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Message-ID: <20190412165112.GB28199@rdna-mbp>
Date:   Fri, 12 Apr 2019 16:51:14 +0000
From:   Andrey Ignatov <rdna@...com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        "Network Development" <netdev@...r.kernel.org>
Subject: Re: [PATCH 8/9] bpf: Check address length before reading address
 family

Alexei Starovoitov <alexei.starovoitov@...il.com> [Fri, 2019-04-12 09:20 -0700]:
> On Fri, Apr 12, 2019 at 3:56 AM Tetsuo Handa
> <penguin-kernel@...ove.sakura.ne.jp> wrote:
> >
> > KMSAN will complain if valid address length passed to bpf_bind() is
> > shorter than sizeof("struct sockaddr"->sa_family) bytes.
> >
> > Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> > ---
> >  net/core/filter.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 41f633cf4fc1..b9089fda4367 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -4458,6 +4458,8 @@ BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
> >          * Only binding to IP is supported.
> >          */
> >         err = -EINVAL;
> > +       if (addr_len < offsetofend(struct sockaddr, sa_family))
> > +               return err;
> 
> the verifier will check that addr_len is not zero,
> but it can be one byte, so it's a good check.
> Thanks!

True, I missed this corner-case. Thanks for fixing.

Acked-by: Andrey Ignatov <rdna@...com>


> >         if (addr->sa_family == AF_INET) {
> >                 if (addr_len < sizeof(struct sockaddr_in))
> >                         return err;
> > --
> > 2.16.5
> >

-- 
Andrey Ignatov