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From: Eric van Gyzen <vangyzen@FreeBSD.org>
Date: Fri, 2 Oct 2015 15:07:03 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r288500 - stable/9/sbin/dmesg
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Author: vangyzen
Date: Fri Oct  2 15:07:02 2015
New Revision: 288500
URL: https://svnweb.freebsd.org/changeset/base/288500

Log:
  MFC r281787
  
  dmesg: accommodate message buffer growth between the sysctl calls
  
  Allocate 12.5% extra space to avoid ENOMEM when the message buffer
  is growing steadily.
  
  Reported by:    Steve Wahl <steve_wahl@dell.com> (and tested)
  Approved by:    kib (mentor until recently)
  Obtained from:  Dell Inc.

Modified:
  stable/9/sbin/dmesg/dmesg.c
Directory Properties:
  stable/9/sbin/dmesg/   (props changed)

Modified: stable/9/sbin/dmesg/dmesg.c
==============================================================================
--- stable/9/sbin/dmesg/dmesg.c	Fri Oct  2 14:36:41 2015	(r288499)
+++ stable/9/sbin/dmesg/dmesg.c	Fri Oct  2 15:07:02 2015	(r288500)
@@ -112,6 +112,9 @@ main(int argc, char *argv[])
 		 */
 		if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
 			err(1, "sysctl kern.msgbuf");
+		/* Allocate extra room for growth between the sysctl calls. */
+		buflen += buflen/8;
+		/* Allocate more than sysctl sees, for room to append \n\0. */
 		if ((bp = malloc(buflen + 2)) == NULL)
 			errx(1, "malloc failed");
 		if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)