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authorVishal Goel <vishal.goel@samsung.com>2016-11-23 08:01:08 +0300
committerCasey Schaufler <casey@schaufler-ca.com>2017-01-10 20:47:20 +0300
commit3c7ce3427106f0fa2d8593f9fd8f82c494215782 (patch)
tree982ee2c19f059bbd1377d0345006a9f87eb7b9ee /security/smack
parent916cafdc95843fb9af5fd5f83ca499d75473d107 (diff)
downloadlinux-3c7ce3427106f0fa2d8593f9fd8f82c494215782.tar.xz
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>
Diffstat (limited to 'security/smack')
-rw-r--r--security/smack/smack_lsm.c20
1 files changed, 15 insertions, 5 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 94dc9d406ce3..b76696b84e5c 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 @@ static void smk_ipv6_port_label(struct socket *sock, struct sockaddr *address)
* 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 @@ static void smk_ipv6_port_label(struct socket *sock, struct sockaddr *address)
* 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 @@ static void smk_ipv6_port_label(struct socket *sock, struct sockaddr *address)
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 @@ static int smk_ipv6_port_check(struct sock *sk, struct sockaddr_in6 *address,
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 @@ static int smk_ipv6_port_check(struct sock *sk, struct sockaddr_in6 *address,
ssp->smk_packet = spp->smk_out;
break;
}
+ rcu_read_unlock();
return smk_ipv6_check(skp, object, address, act);
}