Re: general protection fault in sctp_assoc_rwnd_increase

[Xin Long <lucien.xin@xxxxxxxxx>]

On Sat, Mar 16, 2019 at 10:09 PM syzbot
<syzbot+85e0b422ff140b03672a@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> syzbot has bisected this bug to:
>
> commit 89664c623617b1d34447a927ac7871ddf3db29d3
> Author: Xin Long <lucien.xin@xxxxxxxxx>
> Date:   Sun Mar 3 09:54:53 2019 +0000
>
>      sctp: sctp_sock_migrate() returns error if sctp_bind_addr_dup() fails
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17b17777200000
> start commit:   89664c62 sctp: sctp_sock_migrate() returns error if sctp_b..
> git tree:       upstream
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=14717777200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=10717777200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b613f0327d980b6b
> dashboard link: https://syzkaller.appspot.com/bug?extid=85e0b422ff140b03672a
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12613b13200000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f1884d200000
>
> Reported-by: syzbot+85e0b422ff140b03672a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 89664c62 ("sctp: sctp_sock_migrate() returns error if
> sctp_bind_addr_dup() fails")

sctp_copy_descendant() coplied sctp_sock->pd_lobby. we should fix it with:
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 06c6f4a..e0857dd 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9175,7 +9175,7 @@ static inline void sctp_copy_descendant(struct
sock *sk_to,
 {
  int ancestor_size = sizeof(struct inet_sock) +
      sizeof(struct sctp_sock) -
-     offsetof(struct sctp_sock, auto_asconf_list);
+     offsetof(struct sctp_sock, pd_lobby);

  if (sk_from->sk_family == PF_INET6)
  ancestor_size += sizeof(struct ipv6_pinfo);