Implement issetugid syscall

Implement issetugid syscall and provide a test. This gets rid of the
scary "Unsecure. Implement me" warning during compilation.

servers/pm/exec.c

@@ -81,16 +81,30 @@ PUBLIC int do_exec_newmem()
 	if (r != OK)
 		panic("do_exec_newmem: sys_datacopy failed: %d", r);
 
-	if((r=vm_exec_newmem(proc_e, &args, sizeof(args), &stack_top, &flags)) == OK) {
-		allow_setuid= 0;                /* Do not allow setuid execution */  
+	if ((r = vm_exec_newmem(proc_e, &args, sizeof(args), &stack_top,
+				&flags)) == OK) {
+		allow_setuid = 0;	/* Do not allow setuid execution */
+		rmp->mp_flags &= ~TAINTED;	/* By default not tainted */
 
 		if (rmp->mp_tracer == NO_TRACER) {
 			/* Okay, setuid execution is allowed */
-			allow_setuid= 1;
+			allow_setuid = 1;
+
 			rmp->mp_effuid = args.new_uid;
 			rmp->mp_effgid = args.new_gid;
 		}
 
+		/* A process is considered 'tainted' when it's executing with
+		 * setuid or setgid bit set, or when the real{u,g}id doesn't
+		 * match the eff{u,g}id, respectively. */
+		if (allow_setuid && args.setugid) {
+			/* Program has setuid and/or setgid bits set */
+			rmp->mp_flags |= TAINTED;
+		} else if (rmp->mp_effuid != rmp->mp_realuid ||
+			   rmp->mp_effgid != rmp->mp_realgid) {
+			rmp->mp_flags |= TAINTED;
+		}
+
 		/* System will save command line for debugging, ps(1) output, etc. */
 		strncpy(rmp->mp_name, args.progname, PROC_NAME_LEN-1);
 		rmp->mp_name[PROC_NAME_LEN-1] = '\0';

servers/pm/forkexit.c

@@ -103,7 +103,7 @@ PUBLIC int do_fork()
   }
 
   /* Inherit only these flags. In normal fork(), PRIV_PROC is not inherited. */
-  rmc->mp_flags &= (IN_USE|DELAY_CALL);
+  rmc->mp_flags &= (IN_USE|DELAY_CALL|TAINTED);
   rmc->mp_child_utime = 0;		/* reset administration */
   rmc->mp_child_stime = 0;		/* reset administration */
   rmc->mp_exitstatus = 0;

servers/pm/getset.c

@@ -18,7 +18,8 @@
  *===========================================================================*/
 PUBLIC int do_get()
 {
-/* Handle GETUID, GETGID, GETGROUPS, GETGROUPS_O, GETPID, GETPGRP, GETSID.
+/* Handle GETUID, GETGID, GETGROUPS, GETGROUPS_O, GETPID, GETPGRP, GETSID,
+   ISSETUGID.
  */
 
   register struct mproc *rmp = mp;
@@ -103,6 +104,10 @@ PUBLIC int do_get()
 			r = target->mp_procgrp;
 		break;
 	}
+	case ISSETUGID:
+		r = !!(rmp->mp_flags & TAINTED);
+		break;
+
 	default:
 		r = EINVAL;
 		break;	

servers/pm/mproc.h

@@ -91,5 +91,6 @@ EXTERN struct mproc {
 #define TRACE_EXIT	0x08000	/* tracer is forcing this process to exit */
 #define TRACE_ZOMBIE	0x10000	/* waiting for tracer to issue WAIT call */
 #define DELAY_CALL	0x20000	/* waiting for call before sending signal */
+#define TAINTED		0x40000 /* process is 'tainted' */
 
 #define MP_MAGIC	0xC0FFEE0

servers/pm/table.c

@@ -117,7 +117,7 @@ _PROTOTYPE (int (*call_vec[]), (void) ) = {
 	do_procstat,	/* 103 = procstat */
 	do_getprocnr,	/* 104 = getprocnr */
 	no_sys,		/* 105 = unused */
-	no_sys,		/* 106 = unused */
+	do_get,		/* 106 = issetugid */
 	do_getepinfo_o,	/* 107 = getepinfo XXX: old implementation*/
 	do_adddma,	/* 108 = adddma */
 	do_deldma,	/* 109 = deldma */