bin/61084: nfsd sometimes exits prematurely during port-scan

[Bjoern Groenvall]

>Number:         61084
>Category:       bin
>Synopsis:       nfsd sometimes exits prematurely during port-scan
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jan 08 09:00:32 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Bjoern Groenvall
>Release:        FreeBSD 5.2-RC i386
>Organization:
SICS
>Environment:
System: FreeBSD dim.sics.se 5.2-RC FreeBSD 5.2-RC #1: Fri Dec 19 16:32:35 CET 2003     root at dim.sics.se:/usr/src/sys/i386/compile/DIM  i386

>Description:

When an NFS server is port-scanned nfsd sometimes exits. This has happened
3 times the last few weeks.

Nfsd has been written to exit when accept(2) fails. Unfortunately
accept can sometimes make a "normal" return with errno ECONNABORTED
and in this case nfsd exits prematurely (see below).

Dec 22 16:25:59 dim kernel: Limiting closed port RST response from 363 to 200 packets/sec
Dec 22 16:25:59 dim nfsd[417]: accept failed: Software caused connection abort
Dec 22 16:26:00 dim kernel: Limiting closed port RST response from 215 to 200 packets/sec

Dec 28 08:26:43 dim kernel: Limiting closed port RST response from 325 to 200 packets/sec
Dec 28 08:26:43 dim nfsd[36538]: accept failed: Software caused connection abort
Dec 28 08:26:45 dim kernel: Limiting closed port RST response from 431 to 200 packets/sec

Jan  7 00:37:12 dim kernel: Limiting closed port RST response from 305 to 200 packets/sec
Jan  7 00:37:12 dim nfsd[89133]: accept failed: Software caused connection abort
Jan  7 00:37:14 dim kernel: Limiting closed port RST response from 371 to 200 packets/sec


>How-To-Repeat:

Unknown. Perhaps possible using a port-scan program of some sort.

>Fix:

This is a sample fix that also handles rare "normal" returns with errno EINTR.

--- nfsd.c.orig	Thu Jul 25 08:18:22 2002
+++ nfsd.c	Wed Jan  7 18:02:18 2004
@@ -658,6 +658,8 @@
 			if (select(maxsock + 1,
 			    &ready, NULL, NULL, NULL) < 1) {
 				syslog(LOG_ERR, "select failed: %m");
+				if (errno == EINTR)
+					continue;
 				nfsd_exit(1);
 			}
 		}
@@ -668,6 +670,9 @@
 					if ((msgsock = accept(tcpsock,
 					    (struct sockaddr *)&inetpeer, &len)) < 0) {
 						syslog(LOG_ERR, "accept failed: %m");
+						if (errno == ECONNABORTED ||
+						    errno == EINTR)
+							continue;
 						nfsd_exit(1);
 					}
 					memset(inetpeer.sin_zero, 0,
@@ -688,6 +693,9 @@
 					    &len)) < 0) {
 						syslog(LOG_ERR,
 						     "accept failed: %m");
+						if (errno == ECONNABORTED ||
+						    errno == EINTR)
+							continue;
 						nfsd_exit(1);
 					}
 					if (setsockopt(msgsock, SOL_SOCKET,



>Release-Note:
>Audit-Trail:
>Unformatted: