On Sun, Mar 03, 2019 at 05:54:55PM +0800, Xin Long wrote:
> New ep's auth_hmacs should be set if old ep's is set, in case that
> net->sctp.auth_enable has been changed to 0 by users and new ep's
> auth_hmacs couldn't be set in sctp_endpoint_init().
>
> It can even crash kernel by doing:
>
> 1. on server: sysctl -w net.sctp.auth_enable=1,
> sysctl -w net.sctp.addip_enable=1,
> sysctl -w net.sctp.addip_noauth_enable=0,
> listen() on server,
> sysctl -w net.sctp.auth_enable=0.
> 2. on client: connect() to server.
> 3. on server: accept() the asoc,
> sysctl -w net.sctp.auth_enable=1.
> 4. on client: send() asconf packet to server.
>
> The call trace:
>
> [ 245.280251] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> [ 245.286872] RIP: 0010:sctp_auth_calculate_hmac+0xa3/0x140 [sctp]
> [ 245.304572] Call Trace:
> [ 245.305091] <IRQ>
> [ 245.311287] sctp_sf_authenticate+0x110/0x160 [sctp]
> [ 245.312311] sctp_sf_eat_auth+0xf2/0x230 [sctp]
> [ 245.313249] sctp_do_sm+0x9a/0x2d0 [sctp]
> [ 245.321483] sctp_assoc_bh_rcv+0xed/0x1a0 [sctp]
> [ 245.322495] sctp_rcv+0xa66/0xc70 [sctp]
>
> It's because the old ep->auth_hmacs wasn't copied to the new ep while
> ep->auth_hmacs is used in sctp_auth_calculate_hmac() when processing
> the incoming auth chunks, and it should have been done when migrating
> sock.
>
> Reported-by: Ying Xu <yinxu@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/socket.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 22adb8d..def3335 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -8978,6 +8978,16 @@ static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
> if (err)
> return err;
>
> + /* New ep's auth_hmacs should be set if old ep's is set, in case
> + * that net->sctp.auth_enable has been changed to 0 by users and
> + * new ep's auth_hmacs couldn't be set in sctp_endpoint_init().
> + */
> + if (oldsp->ep->auth_hmacs) {
> + err = sctp_auth_init_hmacs(newsp->ep, GFP_KERNEL);
> + if (err)
> + return err;
> + }
> +
> /* Move any messages in the old socket's receive queue that are for the
> * peeled off association to the new socket's receive queue.
> */
> --
> 2.1.0
>
>
Acked-by: Neil Horman <nhorman@xxxxxxxxxx>
