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Wed, 04 Nov 2020 19:49:12 -0800 (PST) Received: by localhost.localdomain (Postfix, from userid 1000) id DAD41C639F; Thu, 5 Nov 2020 00:49:09 -0300 (-03) Date: Thu, 5 Nov 2020 00:49:09 -0300 From: Marcelo Ricardo Leitner To: Xin Long Cc: network dev , linux-sctp@vger.kernel.org, Neil Horman , davem@davemloft.net, Jakub Kicinski Subject: Re: [PATCH net-next] sctp: bring inet(6)_skb_parm back to sctp_input_cb Message-ID: <20201105034909.GJ11030@localhost.localdomain> References: <136c1a7a419341487c504be6d1996928d9d16e02.1604472932.git.lucien.xin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <136c1a7a419341487c504be6d1996928d9d16e02.1604472932.git.lucien.xin@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-sctp@vger.kernel.org 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: > [ ] > [ ] 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 Acked-by: Marcelo Ricardo Leitner Thanks Xin.