[PATCH] This patch fixes the synchronization issue in IPv6 implementation. Previously there was no synchronization mechanism used while accessing(adding/reading/deletion) smk_ipv6_port_list. It could be possible that when one thread is reading the list, at the same time another thread is adding/deleting in the list.So it is possible that reader thread will read the inaccurate or incomplete list. So to make sure that reader thread will read the accurate list, rcu mechanism has been used while accessing the list.RCU allows readers to access a data structure even when it is in the process of being updated
Signed-off-by: Vishal Goel <[email protected]> Himanshu Shukla <[email protected]> --- security/smack/smack_lsm.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index f1b17a4..87f0f0a 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -52,6 +52,7 @@ #define SMK_RECEIVING 1 #define SMK_SENDING 2 +DEFINE_MUTEX(smack_ipv6_lock); LIST_HEAD(smk_ipv6_port_list); static struct kmem_cache *smack_inode_cache; @@ -2233,17 +2234,20 @@ 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; } @@ -2259,16 +2263,18 @@ 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. */ @@ -2281,7 +2287,9 @@ 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; } @@ -2337,7 +2345,8 @@ static int smk_ipv6_port_check(struct sock *sk, struct sockaddr_in6 *address, goto auditout; } - 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; @@ -2345,6 +2354,7 @@ static int smk_ipv6_port_check(struct sock *sk, struct sockaddr_in6 *address, ssp->smk_packet = spp->smk_out; break; } + rcu_read_unlock(); auditout: -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
