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Commit 3168b078 authored by Satyam Sharma's avatar Satyam Sharma Committed by Steven Whitehouse
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[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: default avatarSatyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: default avatarDavid Teigland <teigland@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent b524fe64

fs/dlm/config.c

+11 −4
Original line number Diff line number Diff line
@@ -748,9 +748,16 @@ static ssize_t node_weight_write(struct node *nd, const char *buf, size_t len) 


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 @@ static struct comm *get_comm(int nodeid, struct sockaddr_storage *addr) 
			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;

}