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In snmp_hostres, device_map table is used for consistent device table

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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
This commit is contained in:
Mikolaj Golub 2012-09-17 07:32:53 +00:00
parent a7dc3573ca
commit 16c3b091ae
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=240595
1 changed files with 6 additions and 0 deletions
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6
usr.sbin/bsnmpd/modules/snmp_hostres/hostres_diskstorage_tbl.c
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@ -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;