SMACK: Add the rcu synchronization mechanism in ipv6 hooks
Add the rcu synchronization mechanism for accessing smk_ipv6_port_list
in smack IPv6 hooks. Access to the port list is vulnerable to a race
condition issue,it does not apply proper synchronization methods while
working on critical section. It is possible that when one thread is
reading the list, at the same time another thread is modifying the
same port list, which can cause the major problems.
To ensure proper synchronization between two threads, rcu mechanism
has been applied while accessing and modifying the port list. RCU will
also not affect the performance, as there are more accesses than
modification where RCU is most effective synchronization mechanism.
Signed-off-by: Vishal Goel <vishal.goel@samsung.com>
Signed-off-by: Himanshu Shukla <himanshu.sh@samsung.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 94dc9d4..b76696b 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -52,6 +52,7 @@
#define SMK_SENDING 2
#ifdef SMACK_IPV6_PORT_LABELING
+DEFINE_MUTEX(smack_ipv6_lock);
static LIST_HEAD(smk_ipv6_port_list);
#endif
static struct kmem_cache *smack_inode_cache;
@@ -2603,17 +2604,20 @@
* on the bound socket. Take the changes to the port
* as well.
*/
- list_for_each_entry(spp, &smk_ipv6_port_list, list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(spp, &smk_ipv6_port_list, list) {
if (sk != spp->smk_sock)
continue;
spp->smk_in = ssp->smk_in;
spp->smk_out = ssp->smk_out;
+ rcu_read_unlock();
return;
}
/*
* A NULL address is only used for updating existing
* bound entries. If there isn't one, it's OK.
*/
+ rcu_read_unlock();
return;
}
@@ -2629,16 +2633,18 @@
* Look for an existing port list entry.
* This is an indication that a port is getting reused.
*/
- list_for_each_entry(spp, &smk_ipv6_port_list, list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(spp, &smk_ipv6_port_list, list) {
if (spp->smk_port != port)
continue;
spp->smk_port = port;
spp->smk_sock = sk;
spp->smk_in = ssp->smk_in;
spp->smk_out = ssp->smk_out;
+ rcu_read_unlock();
return;
}
-
+ rcu_read_unlock();
/*
* A new port entry is required.
*/
@@ -2651,7 +2657,9 @@
spp->smk_in = ssp->smk_in;
spp->smk_out = ssp->smk_out;
- list_add(&spp->list, &smk_ipv6_port_list);
+ mutex_lock(&smack_ipv6_lock);
+ list_add_rcu(&spp->list, &smk_ipv6_port_list);
+ mutex_unlock(&smack_ipv6_lock);
return;
}
@@ -2702,7 +2710,8 @@
return 0;
port = ntohs(address->sin6_port);
- list_for_each_entry(spp, &smk_ipv6_port_list, list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(spp, &smk_ipv6_port_list, list) {
if (spp->smk_port != port)
continue;
object = spp->smk_in;
@@ -2710,6 +2719,7 @@
ssp->smk_packet = spp->smk_out;
break;
}
+ rcu_read_unlock();
return smk_ipv6_check(skp, object, address, act);
}