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From: Mikolaj Golub <trociny@FreeBSD.org>
Date: Mon, 17 Sep 2012 07:32:54 +0000 (UTC)
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Subject: svn commit: r240595 - head/usr.sbin/bsnmpd/modules/snmp_hostres
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Author: trociny
Date: Mon Sep 17 07:32:53 2012
New Revision: 240595
URL: http://svn.freebsd.org/changeset/base/240595

Log:
  In snmp_hostres, device_map table is used for consistent device table
  indexing. When a device has gone it is not removed from device_map
  table but just its entry_p field is set to NULL.
  
  So when traversing device_map in disk_OS_get_ATA_disks() and
  disk_OS_get_MD_disks() check for entry_p being NULL, otherwise the
  bsnmpd crash is possible when a removed map entry is dereferenced.
  
  Before the fix, for disk_OS_get_ATA_disks() the crash could be easily
  reproduced running:
  
    atacontrol detach ata1
  
  The crash was not observed in disk_OS_get_MD_disks() because currently
  snmp_hostres does no see md(4) disks: to get the device list it uses
  devinfo(3), which does not return md devices.
  
  Reported by:	Miroslav Lachman 000.fbsd quip.cz
  MFC after:	1 week

Modified:
  head/usr.sbin/bsnmpd/modules/snmp_hostres/hostres_diskstorage_tbl.c

Modified: head/usr.sbin/bsnmpd/modules/snmp_hostres/hostres_diskstorage_tbl.c
==============================================================================
--- head/usr.sbin/bsnmpd/modules/snmp_hostres/hostres_diskstorage_tbl.c	Mon Sep 17 07:14:07 2012	(r240594)
+++ head/usr.sbin/bsnmpd/modules/snmp_hostres/hostres_diskstorage_tbl.c	Mon Sep 17 07:32:53 2012	(r240595)
@@ -287,6 +287,9 @@ disk_OS_get_ATA_disks(void)
 
 	/* Walk over the device table looking for ata disks */
 	STAILQ_FOREACH(map, &device_map, link) {
+		/* Skip deleted entries. */
+		if (map->entry_p == NULL)
+			continue;
 		for (found = lookup; found->media != DSM_UNKNOWN; found++) {
 			if (strncmp(map->name_key, found->dev_name,
 			    strlen(found->dev_name)) != 0)
@@ -345,6 +348,9 @@ disk_OS_get_MD_disks(void)
 
 	/* Look for md devices */
 	STAILQ_FOREACH(map, &device_map, link) {
+		/* Skip deleted entries. */
+		if (map->entry_p == NULL)
+			continue;
 		if (sscanf(map->name_key, "md%d", &unit) != 1)
 			continue;