Re: Race condition in smtpserver?

[Swen Thuemmler <swen@uni-paderborn.de>]

On Thu, 6 Nov 1997, Swen Thuemmler wrote:

> The patch is below, I think it is correct.

Since the patch is very large because i changend indentation, here is a
minimal patch (diff -bu):

diff -ubr zmailer-2.99.49p8.orig/smtpserver/smtpserver.c zmailer-2.99.49p8/smtpserver/smtpserver.c
--- zmailer-2.99.49p8.orig/smtpserver/smtpserver.c	Tue Oct 14 01:21:56 1997
+++ zmailer-2.99.49p8/smtpserver/smtpserver.c	Thu Nov  6 11:06:47 1997
@@ -757,6 +757,12 @@
 
 	    sameipcount = childsameip(&SS.raddr);
 
+	    /* We simply -- and FAST -- reject the
+	       remote when it exceeds 4 times the
+	       limit */
+	    if (sameipcount > 4 * MaxSameIpSource) {
+		close(msgfd);
+	    } else {
 	    if ((childpid = fork()) < 0) {	/* can't fork! */
 		close(msgfd);
 		fprintf(stderr,
@@ -768,14 +774,6 @@
 		close(s);	/* Listening socket.. */
 		pid = getpid();
 
-		/* We query, and warn the remote when
-		   the count exceeds the limit, and we
-		   simply -- and FAST -- reject the
-		   remote when it exceeds 4 times the
-		   limit */
-		if (sameipcount > 4 * MaxSameIpSource)
-		    exit(0);
-
 		if (msgfd != 0)
 		    dup2(msgfd, 0);
 		dup2(0, 1);
@@ -849,6 +847,9 @@
 		    strcpy(msg, "450 Come again latter\r\n");
 		    len = strlen(msg);
 		    write(msgfd, msg, len);
+			sleep(1); /* not so fast, but tries to avoid a race
+				   * condition: the child may exit before the
+				   * parent calls childregister - bummer */
 		    exit(0);	/* Now exit.. */
 		}
 		smtpserver(&SS, 1);
@@ -856,9 +857,11 @@
 		if (routerpid > 0)
 		    killr(&SS, routerpid);
 		_exit(0);
-	    } else
+		} else {
 		close(msgfd);
+		}
 	    childregister(childpid, &SS.raddr);
+	    }
 	}
     }
 #else				/* !USE_INET */