Apply by doing
       cd /usr/src/usr.sbin/lpr/common_source
       patch -p0 < rmjob.patch

And then to rebuild and install
       cd .. && make && make install

Index: common_source/rmjob.c
===================================================================
RCS file: /cvs/src/usr.sbin/lpr/common_source/rmjob.c,v
retrieving revision 1.8
diff -u -r1.8 rmjob.c
--- rmjob.c     1997/07/23 22:12:12     1.8
+++ rmjob.c     1998/04/22 14:42:23
@@ -333,14 +333,14 @@
        */
       fflush(stdout);

-       (void)snprintf(buf, sizeof(buf), "\5%s %s", RP, all ? "-all" : person);
-       cp = buf;
-       for (i = 0; i < users && cp-buf+1+strlen(user[i]) < sizeof buf; i++) {
+       (void)snprintf(buf, sizeof(buf)-2, "\5%s %s", RP, all ? "-all" : person);
+       cp = buf + strlen(buf);
+       for (i = 0; i < users && cp-buf+1+strlen(user[i]) < sizeof buf - 2; i++) {
               cp += strlen(cp);
               *cp++ = ' ';
               strcpy(cp, user[i]);
       }
-       for (i = 0; i < requests && cp-buf+10 < sizeof(buf) - 1; i++) {
+       for (i = 0; i < requests && cp-buf+10 < sizeof(buf) - 2; i++) {
               cp += strlen(cp);
               (void) sprintf(cp, " %d", requ[i]);
       }