glibc/0018-resolv-Always-set-resplen2-out-parameter-in-send_dg-.patch

2016-03-25  Florian Weimer  <fweimer@redhat.com>

	[BZ #19791]
	* resolv/res_send.c (close_and_return_error): New function.
	(send_dg): Initialize *resplen2 after reopen failure.  Call
	close_and_return_error for error returns.  On error paths without
	__res_iclose, initialze *resplen2 explicitly.  Update comment for
	successful return.

Index: glibc-2.23/NEWS
===================================================================
--- glibc-2.23.orig/NEWS
+++ glibc-2.23/NEWS
@@ -17,6 +17,7 @@ The following bugs are resolved with thi
   [19758] Or bit_Prefer_MAP_32BIT_EXEC in EXTRA_LD_ENVVARS
   [19759] Don't inline mempcpy for x86
   [19762] Use HAS_ARCH_FEATURE with Fast_Rep_String
+  [19791] Assertion failure in res_query.c with un-connectable name server addresses
   [19792] MIPS: backtrace yields infinite backtrace with makecontext
   [19822] libm.so install clobbers old version
 
Index: glibc-2.23/resolv/res_send.c
===================================================================
--- glibc-2.23.orig/resolv/res_send.c
+++ glibc-2.23/resolv/res_send.c
@@ -649,6 +649,18 @@ get_nsaddr (res_state statp, int n)
     return (struct sockaddr *) (void *) &statp->nsaddr_list[n];
 }
 
+/* Close the resolver structure, assign zero to *RESPLEN2 if RESPLEN2
+   is not NULL, and return zero.  */
+static int
+__attribute__ ((warn_unused_result))
+close_and_return_error (res_state statp, int *resplen2)
+{
+  __res_iclose(statp, false);
+  if (resplen2 != NULL)
+    *resplen2 = 0;
+  return 0;
+}
+
 /* The send_vc function is responsible for sending a DNS query over TCP
    to the nameserver numbered NS from the res_state STATP i.e.
    EXT(statp).nssocks[ns].  The function supports sending both IPv4 and
@@ -1114,7 +1126,11 @@ send_dg(res_state statp,
  retry_reopen:
 	retval = reopen (statp, terrno, ns);
 	if (retval <= 0)
-		return retval;
+	  {
+	    if (resplen2 != NULL)
+	      *resplen2 = 0;
+	    return retval;
+	  }
  retry:
 	evNowTime(&now);
 	evConsTime(&timeout, seconds, 0);
@@ -1127,8 +1143,6 @@ send_dg(res_state statp,
 	int recvresp2 = buf2 == NULL;
 	pfd[0].fd = EXT(statp).nssocks[ns];
 	pfd[0].events = POLLOUT;
-	if (resplen2 != NULL)
-	  *resplen2 = 0;
  wait:
 	if (need_recompute) {
 	recompute_resend:
@@ -1136,9 +1150,7 @@ send_dg(res_state statp,
 		if (evCmpTime(finish, now) <= 0) {
 		poll_err_out:
 			Perror(statp, stderr, "poll", errno);
-		err_out:
-			__res_iclose(statp, false);
-			return (0);
+			return close_and_return_error (statp, resplen2);
 		}
 		evSubTime(&timeout, &finish, &now);
 		need_recompute = 0;
@@ -1185,7 +1197,9 @@ send_dg(res_state statp,
 		  }
 
 		*gotsomewhere = 1;
-		return (0);
+		if (resplen2 != NULL)
+		  *resplen2 = 0;
+		return 0;
 	}
 	if (n < 0) {
 		if (errno == EINTR)
@@ -1253,7 +1267,7 @@ send_dg(res_state statp,
 
 		      fail_sendmmsg:
 			Perror(statp, stderr, "sendmmsg", errno);
-			goto err_out;
+			return close_and_return_error (statp, resplen2);
 		      }
 		  }
 		else
@@ -1271,7 +1285,7 @@ send_dg(res_state statp,
 		      if (errno == EINTR || errno == EAGAIN)
 			goto recompute_resend;
 		      Perror(statp, stderr, "send", errno);
-		      goto err_out;
+		      return close_and_return_error (statp, resplen2);
 		    }
 		  just_one:
 		    if (nwritten != 0 || buf2 == NULL || single_request)
@@ -1349,7 +1363,7 @@ send_dg(res_state statp,
 				goto wait;
 			}
 			Perror(statp, stderr, "recvfrom", errno);
-			goto err_out;
+			return close_and_return_error (statp, resplen2);
 		}
 		*gotsomewhere = 1;
 		if (__glibc_unlikely (*thisresplenp < HFIXEDSZ))       {
@@ -1360,7 +1374,7 @@ send_dg(res_state statp,
 			       (stdout, ";; undersized: %d\n",
 				*thisresplenp));
 			*terrno = EMSGSIZE;
-			goto err_out;
+			return close_and_return_error (statp, resplen2);
 		}
 		if ((recvresp1 || hp->id != anhp->id)
 		    && (recvresp2 || hp2->id != anhp->id)) {
@@ -1409,7 +1423,7 @@ send_dg(res_state statp,
 				? *thisanssizp : *thisresplenp);
 			/* record the error */
 			statp->_flags |= RES_F_EDNS0ERR;
-			goto err_out;
+			return close_and_return_error (statp, resplen2);
 	}
 #endif
 		if (!(statp->options & RES_INSECURE2)
@@ -1461,10 +1475,10 @@ send_dg(res_state statp,
 			    goto wait;
 			  }
 
-			__res_iclose(statp, false);
 			/* don't retry if called from dig */
 			if (!statp->pfcode)
-				return (0);
+			  return close_and_return_error (statp, resplen2);
+			__res_iclose(statp, false);
 		}
 		if (anhp->rcode == NOERROR && anhp->ancount == 0
 		    && anhp->aa == 0 && anhp->ra == 0 && anhp->arcount == 0) {
@@ -1486,6 +1500,8 @@ send_dg(res_state statp,
 			__res_iclose(statp, false);
 			// XXX if we have received one reply we could
 			// XXX use it and not repeat it over TCP...
+			if (resplen2 != NULL)
+			  *resplen2 = 0;
 			return (1);
 		}
 		/* Mark which reply we received.  */
@@ -1501,21 +1517,22 @@ send_dg(res_state statp,
 					__res_iclose (statp, false);
 					retval = reopen (statp, terrno, ns);
 					if (retval <= 0)
-						return retval;
+					  {
+					    if (resplen2 != NULL)
+					      *resplen2 = 0;
+					    return retval;
+					  }
 					pfd[0].fd = EXT(statp).nssocks[ns];
 				}
 			}
 			goto wait;
 		}
-		/*
-		 * All is well, or the error is fatal.  Signal that the
-		 * next nameserver ought not be tried.
-		 */
+		/* All is well.  We have received both responses (if
+		   two responses were requested).  */
 		return (resplen);
-	} else if (pfd[0].revents & (POLLERR | POLLHUP | POLLNVAL)) {
-		/* Something went wrong.  We can stop trying.  */
-		goto err_out;
-	}
+	} else if (pfd[0].revents & (POLLERR | POLLHUP | POLLNVAL))
+	  /* Something went wrong.  We can stop trying.  */
+	  return close_and_return_error (statp, resplen2);
 	else {
 		/* poll should not have returned > 0 in this case.  */
 		abort ();