[DLM] fix a couple of races
Fix two races in fs/dlm/config.c:
(1) Grab the configfs subsystem semaphore before calling
config_group_find_obj() in get_space(). This solves a potential race
between get_space() and concurrent mkdir(2) or rmdir(2).
(2) Grab a reference on the found config_item _while_ holding the configfs
subsystem semaphore in get_comm(), and not after it. This solves a
potential race between get_comm() and concurrent rmdir(2).
Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/dlm/config.c b/fs/dlm/config.c
index 822abdcd..5a3d390 100644
--- a/fs/dlm/config.c
+++ b/fs/dlm/config.c
@@ -748,9 +748,16 @@
static struct space *get_space(char *name)
{
+ struct config_item *i;
+
if (!space_list)
return NULL;
- return to_space(config_group_find_obj(space_list, name));
+
+ down(&space_list->cg_subsys->su_sem);
+ i = config_group_find_obj(space_list, name);
+ up(&space_list->cg_subsys->su_sem);
+
+ return to_space(i);
}
static void put_space(struct space *sp)
@@ -776,20 +783,20 @@
if (cm->nodeid != nodeid)
continue;
found = 1;
+ config_item_get(i);
break;
} else {
if (!cm->addr_count ||
memcmp(cm->addr[0], addr, sizeof(*addr)))
continue;
found = 1;
+ config_item_get(i);
break;
}
}
up(&clusters_root.subsys.su_sem);
- if (found)
- config_item_get(i);
- else
+ if (!found)
cm = NULL;
return cm;
}