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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Thu, 16 Aug 2012 13:04:21 +0000 (UTC)
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Subject: svn commit: r239329 - head/sys/kern
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Author: kib
Date: Thu Aug 16 13:04:21 2012
New Revision: 239329
URL: http://svn.freebsd.org/changeset/base/239329

Log:
  As a safety measure, disable lowering pid_max too much.
  
  Requested by:	Peter Jeremy <peter@rulingia.com>
  MFC after:	1 week

Modified:
  head/sys/kern/kern_mib.c
  head/sys/kern/subr_param.c

Modified: head/sys/kern/kern_mib.c
==============================================================================
--- head/sys/kern/kern_mib.c	Thu Aug 16 13:01:56 2012	(r239328)
+++ head/sys/kern/kern_mib.c	Thu Aug 16 13:04:21 2012	(r239329)
@@ -510,8 +510,12 @@ sysctl_kern_pid_max(SYSCTL_HANDLER_ARGS)
 		return (error);
 	sx_xlock(&proctree_lock);
 	sx_xlock(&allproc_lock);
-	/* Only permit the values less then PID_MAX. */
-	if (pm > PID_MAX)
+
+	/*
+	 * Only permit the values less then PID_MAX.
+	 * As a safety measure, do not allow to limit the pid_max too much.
+	 */
+	if (pm < 300 || pm > PID_MAX)
 		error = EINVAL;
 	else
 		pid_max = pm;

Modified: head/sys/kern/subr_param.c
==============================================================================
--- head/sys/kern/subr_param.c	Thu Aug 16 13:01:56 2012	(r239328)
+++ head/sys/kern/subr_param.c	Thu Aug 16 13:04:21 2012	(r239329)
@@ -255,10 +255,13 @@ init_param1(void)
 
 	/*
 	 * Only allow to lower the maximal pid.
+	 * Prevent setting up a non-bootable system if pid_max is too low.
 	 */
 	TUNABLE_INT_FETCH("kern.pid_max", &pid_max);
 	if (pid_max > PID_MAX)
 		pid_max = PID_MAX;
+	else if (pid_max < 300)
+		pid_max = 300;
 }
 
 /*