On Mon, Sep 30, 2024 at 04:49:51PM -0400, Xin Long wrote:
> In sctp_listen_start() invoked by sctp_inet_listen(), it should set the
> sk_state back to CLOSED if sctp_autobind() fails due to whatever reason.
>
> Otherwise, next time when calling sctp_inet_listen(), if sctp_sk(sk)->reuse
> is already set via setsockopt(SCTP_REUSE_PORT), sctp_sk(sk)->bind_hash will
> be dereferenced as sk_state is LISTENING, which causes a crash as bind_hash
> is NULL.
>
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> RIP: 0010:sctp_inet_listen+0x7f0/0xa20 net/sctp/socket.c:8617
> Call Trace:
> <TASK>
> __sys_listen_socket net/socket.c:1883 [inline]
> __sys_listen+0x1b7/0x230 net/socket.c:1894
> __do_sys_listen net/socket.c:1902 [inline]
>
> Fixes: 5e8f3f703ae4 ("sctp: simplify sctp listening code")
> Reported-by: syzbot+f4e0f821e3a3b7cee51d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/socket.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 32f76f1298da..078bcb3858c7 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -8557,8 +8557,10 @@ static int sctp_listen_start(struct sock *sk, int backlog)
> */
> inet_sk_set_state(sk, SCTP_SS_LISTENING);
> if (!ep->base.bind_addr.port) {
> - if (sctp_autobind(sk))
> + if (sctp_autobind(sk)) {
> + inet_sk_set_state(sk, SCTP_SS_CLOSED);
> return -EAGAIN;
> + }
> } else {
> if (sctp_get_port(sk, inet_sk(sk)->inet_num)) {
> inet_sk_set_state(sk, SCTP_SS_CLOSED);
Then AFAICT the end of the function needs a patch as well, because it
returns what could be an error directly, without undoing this:
WRITE_ONCE(sk->sk_max_ack_backlog, backlog);
return sctp_hash_endpoint(ep);
}
