linux-kernel - Re: [PATCH net] xfrm: Fix xfrm sel prefix length validation

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Date:   Mon, 20 May 2019 22:35:24 +0530
From:   Anirudh Gupta <anirudhrudr@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Anirudh Gupta <anirudh.gupta@...hos.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] xfrm: Fix xfrm sel prefix length validation

Hi Herbert,
Yes, I notice that is the only verification of p->family from userspace.
However, the underlying conditions added in commit '07bf7908950a',
validates the selector src/dest prefix len.

So, In case when adding a new SA entry, the family of Selector src/dst
is IPv6 and state id src/dst family is IPv4.
Then, the IPv6 selector prefix verification falls in IPv4 switch case.
This results in not being able to provide prefix length of more than
32, even for IPv6 src/dst.

The above mentioned behaviour can easily be reproduced using below
command having IPv6 selector src/dst with greater than 32 prefix
length.
ip xfrm state add src 1.1.6.1 dst 1.1.6.2 proto esp spi 4260196 \
reqid 20004 mode tunnel aead "rfc4106(gcm(aes))" \
0x1111016400000000000000000000000044440001 128 \
sel src 1011:1:4::2/128 sel dst 1021:1:4::2/128 dev Port5

Please let me know, if I fail to explain my point or I am overlooking anything.

Thanks & Regards,
Anirudh

On Mon, May 20, 2019 at 9:02 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> On Mon, May 20, 2019 at 03:01:56PM +0530, Anirudh Gupta wrote:
> >
> > diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
> > index eb8d14389601..fc2a8c08091b 100644
> > --- a/net/xfrm/xfrm_user.c
> > +++ b/net/xfrm/xfrm_user.c
> > @@ -149,7 +149,7 @@ static int verify_newsa_info(struct xfrm_usersa_info *p,
> >       int err;
> >
> >       err = -EINVAL;
> > -     switch (p->family) {
> > +     switch (p->sel.family) {
> >       case AF_INET:
> >               if (p->sel.prefixlen_d > 32 || p->sel.prefixlen_s > 32)
> >                       goto out;
>
> You just removed the only verification of p->family...
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- 
Regards

Anirudh Gupta