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Date:      Sat, 29 Dec 2018 15:55:44 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r342595 - head/sys/kern
Message-ID:  <201812291555.wBTFtiwj093566@repo.freebsd.org>
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Author: kib
Date: Sat Dec 29 15:55:44 2018
New Revision: 342595
URL: https://svnweb.freebsd.org/changeset/base/342595

Log:
  For hw.{physmem,realmem,usermem} MIBs, clamp instead truncating.
  
  If the memory size does not fit into u_long, current code truncates
  the returned value and returns complete nonsense.  Make the result
  slightly more useful by clamping it at ULONG_MAX.
  
  Reported and tested :	pho
  MFC after:	1 week
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/kern/kern_mib.c

Modified: head/sys/kern/kern_mib.c
==============================================================================
--- head/sys/kern/kern_mib.c	Sat Dec 29 15:49:03 2018	(r342594)
+++ head/sys/kern/kern_mib.c	Sat Dec 29 15:55:44 2018	(r342595)
@@ -46,6 +46,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/jail.h>
 #include <sys/kernel.h>
+#include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/proc.h>
@@ -177,35 +178,45 @@ SYSCTL_PROC(_kern, KERN_ARND, arandom,
 static int
 sysctl_hw_physmem(SYSCTL_HANDLER_ARGS)
 {
-	u_long val;
+	u_long val, p;
 
-	val = ctob(physmem);
+	p = SIZE_T_MAX >> PAGE_SHIFT;
+	if (physmem < p)
+		p = physmem;
+	val = ctob(p);
 	return (sysctl_handle_long(oidp, &val, 0, req));
 }
-
 SYSCTL_PROC(_hw, HW_PHYSMEM, physmem, CTLTYPE_ULONG | CTLFLAG_RD,
-	0, 0, sysctl_hw_physmem, "LU", "");
+    0, 0, sysctl_hw_physmem, "LU", "");
 
 static int
 sysctl_hw_realmem(SYSCTL_HANDLER_ARGS)
 {
-	u_long val;
-	val = ctob(realmem);
+	u_long val, p;
+
+	p = SIZE_T_MAX >> PAGE_SHIFT;
+	if (realmem < p)
+		p = realmem;
+	val = ctob(p);
 	return (sysctl_handle_long(oidp, &val, 0, req));
 }
 SYSCTL_PROC(_hw, HW_REALMEM, realmem, CTLTYPE_ULONG | CTLFLAG_RD,
-	0, 0, sysctl_hw_realmem, "LU", "");
+    0, 0, sysctl_hw_realmem, "LU", "");
+
 static int
 sysctl_hw_usermem(SYSCTL_HANDLER_ARGS)
 {
-	u_long val;
+	u_long val, p, p1;
 
-	val = ctob(physmem - vm_wire_count());
+	p1 = physmem - vm_wire_count();
+	p = SIZE_T_MAX >> PAGE_SHIFT;
+	if (p1 < p)
+		p = p1;
+	val = ctob(p);
 	return (sysctl_handle_long(oidp, &val, 0, req));
 }
-
 SYSCTL_PROC(_hw, HW_USERMEM, usermem, CTLTYPE_ULONG | CTLFLAG_RD,
-	0, 0, sysctl_hw_usermem, "LU", "");
+    0, 0, sysctl_hw_usermem, "LU", "");
 
 SYSCTL_LONG(_hw, OID_AUTO, availpages, CTLFLAG_RD, &physmem, 0, "");

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