SMACK: Add new lock for adding entry in smack master list

"smk_set_access()" function adds a new rule entry in subject label specific
list(rule_list) and in global rule list(smack_rule_list) both. Mutex lock
(rule_lock) is used to avoid simultaneous updates. But this lock is subject
label specific lock. If 2 processes tries to add different rules(i.e with
different subject labels) simultaneously, then both the processes can take
the "rule_lock" respectively. So it will cause a problem while adding
entries in master rule list.
Now a new mutex lock(smack_master_list_lock) has been taken to add entry in
smack_rule_list to avoid simultaneous updates of different rules.

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/smackfs.c b/security/smack/smackfs.c
index 13743a0..366b835 100644 (file)
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -67,6 +67,7 @@ enum smk_inos {
 /*
  * List locks
  */
+static DEFINE_MUTEX(smack_master_list_lock);
 static DEFINE_MUTEX(smack_cipso_lock);
 static DEFINE_MUTEX(smack_ambient_lock);
 static DEFINE_MUTEX(smk_net4addr_lock);
@@ -262,12 +263,16 @@ static int smk_set_access(struct smack_parsed_rule *srp,
                 * it needs to get added for reporting.
                 */
                if (global) {
+                       mutex_unlock(rule_lock);
                        smlp = kzalloc(sizeof(*smlp), GFP_KERNEL);
                        if (smlp != NULL) {
                                smlp->smk_rule = sp;
+                               mutex_lock(&smack_master_list_lock);
                                list_add_rcu(&smlp->list, &smack_rule_list);
+                               mutex_unlock(&smack_master_list_lock);
                        } else
                                rc = -ENOMEM;
+                       return rc;
                }
        }