Messages in this thread | | | From | Yang Xiao <> | Date | Fri, 31 May 2019 11:04:22 +0800 | Subject | Re: [PATCH] ipv6: Prevent overrun when parsing v6 header options |
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On Fri, May 31, 2019 at 1:17 AM Eric Dumazet <eric.dumazet@gmail.com> wrote: > > > > On 5/30/19 8:28 AM, Young Xiao wrote: > > The fragmentation code tries to parse the header options in order > > to figure out where to insert the fragment option. Since nexthdr points > > to an invalid option, the calculation of the size of the network header > > can made to be much larger than the linear section of the skb and data > > is read outside of it. > > > > This vulnerability is similar to CVE-2017-9074. > > > > Signed-off-by: Young Xiao <92siuyang@gmail.com> > > --- > > net/ipv6/mip6.c | 24 ++++++++++++++---------- > > 1 file changed, 14 insertions(+), 10 deletions(-) > > > > diff --git a/net/ipv6/mip6.c b/net/ipv6/mip6.c > > index 64f0f7b..30ed1c5 100644 > > --- a/net/ipv6/mip6.c > > +++ b/net/ipv6/mip6.c > > @@ -263,8 +263,6 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > > u8 **nexthdr) > > { > > u16 offset = sizeof(struct ipv6hdr); > > - struct ipv6_opt_hdr *exthdr = > > - (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1); > > const unsigned char *nh = skb_network_header(skb); > > unsigned int packet_len = skb_tail_pointer(skb) - > > skb_network_header(skb); > > @@ -272,7 +270,8 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > > > > *nexthdr = &ipv6_hdr(skb)->nexthdr; > > > > - while (offset + 1 <= packet_len) { > > + while (offset <= packet_len) { > > + struct ipv6_opt_hdr *exthdr; > > > > switch (**nexthdr) { > > case NEXTHDR_HOP: > > @@ -299,12 +298,15 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, > > return offset; > > } > > > > + if (offset + sizeof(struct ipv6_opt_hdr) > packet_len) > > + return -EINVAL; > > + > > + exthdr = (struct ipv6_opt_hdr *)(nh + offset); > > offset += ipv6_optlen(exthdr); > > *nexthdr = &exthdr->nexthdr; > > - exthdr = (struct ipv6_opt_hdr *)(nh + offset); > > } > > > > - return offset; > > + return -EINVAL; > > } > > > > > Ok, but have you checked that callers have been fixed ?
I've checked the callers. There are two callers: xfrm6_transport_output() and xfrm6_ro_output(). There are checks in both function.
------------------------------------------------------------------------------ hdr_len = x->type->hdr_offset(x, skb, &prevhdr); if (hdr_len < 0) return hdr_len; ------------------------------------------------------------------------------ > > xfrm6_transport_output() seems buggy as well, > unless the skbs are linearized before entering these functions ? I can not understand what you mean about this comment. Could you explain it in more detail.
> > Thanks. > > >
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