Receiving out of band data in unix domain causes panic

[Alex White]

Subject: Using out of band data causes panic(mfree)
Index:	sys/sys/uipc_usrreq.c 4.2BSD

Description:
	Receiving data with MSG_OOB set causes panic in the unix domain.
	soreceive() calls pr_usrreq with a newly allocated mbuf,
	but the code for PRU_RCVOOB is non-existent, hence it always
	frees it, when it returns to soreceive that tries to free it
	again and panics.
Repeat-By:
	Just do an recv with the flag MSG_OOB set in the unix domain.
Fix:
	The following just disallows MSG_OOB in the unix domain, rather
	than making it work. It just causes a return of EOPNOTSUPP
	It hasn't been tested as I don't have an available machine...
*** uipc_usrreq.c	Mon Jan 23 12:25:52 1984
--- /usr/distr/4.2/usr/sys/sys/uipc_usrreq.c	Sun Sep 25 21:06:43 1983
***************
*** 180,186
  			snd->sb_hiwat -= rcv->sb_cc - rcv->sb_hiwat;
  			rcv->sb_hiwat = rcv->sb_cc;
  			sbwakeup(rcv);
- 			m = 0;
  #undef snd
  #undef rcv
  			break;

--- 180,185 -----
  			snd->sb_hiwat -= rcv->sb_cc - rcv->sb_hiwat;
  			rcv->sb_hiwat = rcv->sb_cc;
  			sbwakeup(rcv);
  #undef snd
  #undef rcv
  			break;
***************
*** 188,193
  		default:
  			panic("uipc 4");
  		}
  		break;
  
  	case PRU_ABORT:

--- 187,193 -----
  		default:
  			panic("uipc 4");
  		}
+ 		m = 0;
  		break;
  
  	case PRU_ABORT:
***************
*** 204,211
  /* END UNIMPLEMENTED HOOKS */
  
  	case PRU_RCVOOB:
! 		/* Don't release resources below, sorecieve always does */
! 		return (EOPNOTSUPP);
  
  	case PRU_SENDOOB:
  		/* Release resources below, sosend never does... */

--- 204,210 -----
  /* END UNIMPLEMENTED HOOKS */
  
  	case PRU_RCVOOB:
! 		break;
  
  	case PRU_SENDOOB:
  		break;
***************
*** 208,215
  		return (EOPNOTSUPP);
  
  	case PRU_SENDOOB:
- 		/* Release resources below, sosend never does... */
- 		error = EOPNOTSUPP;
  		break;
  
  	case PRU_SOCKADDR:

--- 207,212 -----
  		break;
  
  	case PRU_SENDOOB:
  		break;
  
  	case PRU_SOCKADDR: