Re: [PATCH net-next] sctp: bring inet(6)_skb_parm back to sctp_input_cb

Jakub Kicinski
2020-11-05T22:29:33Z

On Thu, 5 Nov 2020 00:49:09 -0300 Marcelo Ricardo Leitner wrote:
> On Wed, Nov 04, 2020 at 02:55:32PM +0800, Xin Long wrote:
> > inet(6)_skb_parm was removed from sctp_input_cb by Commit a1dd2cf2f1ae
> > ("sctp: allow changing transport encap_port by peer packets"), as it
> > thought sctp_input_cb->header is not used any more in SCTP.
> >
> > syzbot reported a crash:
> >
> > [ ] BUG: KASAN: use-after-free in decode_session6+0xe7c/0x1580
> > [ ]
> > [ ] Call Trace:
> > [ ] <IRQ>
> > [ ] dump_stack+0x107/0x163
> > [ ] kasan_report.cold+0x1f/0x37
> > [ ] decode_session6+0xe7c/0x1580
> > [ ] __xfrm_policy_check+0x2fa/0x2850
> > [ ] sctp_rcv+0x12b0/0x2e30
> > [ ] sctp6_rcv+0x22/0x40
> > [ ] ip6_protocol_deliver_rcu+0x2e8/0x1680
> > [ ] ip6_input_finish+0x7f/0x160
> > [ ] ip6_input+0x9c/0xd0
> > [ ] ipv6_rcv+0x28e/0x3c0
> >
> > It was caused by sctp_input_cb->header/IP6CB(skb) still used in sctp rx
> > path decode_session6() but some members overwritten by sctp6_rcv().
> >
> > This patch is to fix it by bring inet(6)_skb_parm back to sctp_input_cb
> > and not overwriting it in sctp4/6_rcv() and sctp_udp_rcv().
> >
> > Reported-by: syzbot+5be8aebb1b7dfa90ef31@syzkaller.appspotmail.com
> > Fixes: a1dd2cf2f1ae ("sctp: allow changing transport encap_port by peer packets")
> > Signed-off-by: Xin Long <lucien.xin@gmail.com>
>
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Applied, thanks!