Re: [PATCH net] dccp: check for ccid in ccid_hc_tx_send_packet

[Bragatheswaran Manickavel]

On 30/10/23 14:29, Eric Dumazet wrote:
> On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
> <bragathemanick0908@xxxxxxxxx> wrote:
> > ccid_hc_tx_send_packet might be called with a NULL ccid pointer
> > leading to a NULL pointer dereference
> >
> > Below mentioned commit has similarly changes
> > commit 276bdb82dedb ("dccp: check ccid before dereferencing")
> >
> > Reported-by: syzbot+c71bc336c5061153b502@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
> > Signed-off-by: Bragatheswaran Manickavel <bragathemanick0908@xxxxxxxxx>
> > ---
> >   net/dccp/ccid.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
> > index 105f3734dadb..1015dc2b9392 100644
> > --- a/net/dccp/ccid.h
> > +++ b/net/dccp/ccid.h
> > @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
> >   static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
> >                                           struct sk_buff *skb)
> >   {
> > -       if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> > +       if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> >                  return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
> >          return CCID_PACKET_SEND_AT_ONCE;
> >   }
> > --
> > 2.34.1
> If you are willing to fix dccp, I would make sure that some of
> lockless accesses to dccps_hc_tx_ccid
> are also double checked and fixed.
>
> do_dccp_getsockopt() and dccp_get_info()


Hi Eric,

In both do_dccp_getsockopt() and dccp_get_info(), dccps_hc_rx_ccid are 
checked properly before access.

Thanks,
Bragathe