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

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Date:   Thu, 5 Nov 2020 14:29:27 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>,
        linux-sctp@...r.kernel.org, Neil Horman <nhorman@...driver.com>,
        davem@...emloft.net
Subject: Re: [PATCH net-next] sctp: bring inet(6)_skb_parm back to
 sctp_input_cb

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@...kaller.appspotmail.com
> > Fixes: a1dd2cf2f1ae ("sctp: allow changing transport encap_port by peer packets")
> > Signed-off-by: Xin Long <lucien.xin@...il.com>  
> 
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

Applied, thanks!