Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm...

[~andy/linux] / security / yama / yama_lsm.c

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index b4c29848b49d2ab2741ade9f1aece147ac02e6a3..23414b93771f30ec82ccf76b6cfb49fbed27edef 100644 (file)
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -17,6 +17,7 @@
 #include <linux/ptrace.h>
 #include <linux/prctl.h>
 #include <linux/ratelimit.h>
+#include <linux/workqueue.h>
 
 #define YAMA_SCOPE_DISABLED    0
 #define YAMA_SCOPE_RELATIONAL  1
@@ -29,12 +30,37 @@ static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
 struct ptrace_relation {
        struct task_struct *tracer;
        struct task_struct *tracee;
+       bool invalid;
        struct list_head node;
+       struct rcu_head rcu;
 };
 
 static LIST_HEAD(ptracer_relations);
 static DEFINE_SPINLOCK(ptracer_relations_lock);
 
+static void yama_relation_cleanup(struct work_struct *work);
+static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);
+
+/**
+ * yama_relation_cleanup - remove invalid entries from the relation list
+ *
+ */
+static void yama_relation_cleanup(struct work_struct *work)
+{
+       struct ptrace_relation *relation;
+
+       spin_lock(&ptracer_relations_lock);
+       rcu_read_lock();
+       list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+               if (relation->invalid) {
+                       list_del_rcu(&relation->node);
+                       kfree_rcu(relation, rcu);
+               }
+       }
+       rcu_read_unlock();
+       spin_unlock(&ptracer_relations_lock);
+}
+
 /**
  * yama_ptracer_add - add/replace an exception for this tracer/tracee pair
  * @tracer: the task_struct of the process doing the ptrace
@@ -48,32 +74,34 @@ static DEFINE_SPINLOCK(ptracer_relations_lock);
 static int yama_ptracer_add(struct task_struct *tracer,
                            struct task_struct *tracee)
 {
-       int rc = 0;
-       struct ptrace_relation *added;
-       struct ptrace_relation *entry, *relation = NULL;
+       struct ptrace_relation *relation, *added;
 
        added = kmalloc(sizeof(*added), GFP_KERNEL);
        if (!added)
                return -ENOMEM;
 
-       spin_lock_bh(&ptracer_relations_lock);
-       list_for_each_entry(entry, &ptracer_relations, node)
-               if (entry->tracee == tracee) {
-                       relation = entry;
-                       break;
+       added->tracee = tracee;
+       added->tracer = tracer;
+       added->invalid = false;
+
+       spin_lock(&ptracer_relations_lock);
+       rcu_read_lock();
+       list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+               if (relation->invalid)
+                       continue;
+               if (relation->tracee == tracee) {
+                       list_replace_rcu(&relation->node, &added->node);
+                       kfree_rcu(relation, rcu);
+                       goto out;
                }
-       if (!relation) {
-               relation = added;
-               relation->tracee = tracee;
-               list_add(&relation->node, &ptracer_relations);
        }
-       relation->tracer = tracer;
 
-       spin_unlock_bh(&ptracer_relations_lock);
-       if (added != relation)
-               kfree(added);
+       list_add_rcu(&added->node, &ptracer_relations);
 
-       return rc;
+out:
+       rcu_read_unlock();
+       spin_unlock(&ptracer_relations_lock);
+       return 0;
 }
 
 /**
@@ -84,16 +112,23 @@ static int yama_ptracer_add(struct task_struct *tracer,
 static void yama_ptracer_del(struct task_struct *tracer,
                             struct task_struct *tracee)
 {
-       struct ptrace_relation *relation, *safe;
+       struct ptrace_relation *relation;
+       bool marked = false;
 
-       spin_lock_bh(&ptracer_relations_lock);
-       list_for_each_entry_safe(relation, safe, &ptracer_relations, node)
+       rcu_read_lock();
+       list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+               if (relation->invalid)
+                       continue;
                if (relation->tracee == tracee ||
                    (tracer && relation->tracer == tracer)) {
-                       list_del(&relation->node);
-                       kfree(relation);
+                       relation->invalid = true;
+                       marked = true;
                }
-       spin_unlock_bh(&ptracer_relations_lock);
+       }
+       rcu_read_unlock();
+
+       if (marked)
+               schedule_work(&yama_relation_work);
 }
 
 /**
@@ -217,21 +252,22 @@ static int ptracer_exception_found(struct task_struct *tracer,
        struct task_struct *parent = NULL;
        bool found = false;
 
-       spin_lock_bh(&ptracer_relations_lock);
        rcu_read_lock();
        if (!thread_group_leader(tracee))
                tracee = rcu_dereference(tracee->group_leader);
-       list_for_each_entry(relation, &ptracer_relations, node)
+       list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+               if (relation->invalid)
+                       continue;
                if (relation->tracee == tracee) {
                        parent = relation->tracer;
                        found = true;
                        break;
                }
+       }
 
        if (found && (parent == NULL || task_is_descendant(parent, tracer)))
                rc = 1;
        rcu_read_unlock();
-       spin_unlock_bh(&ptracer_relations_lock);
 
        return rc;
 }
@@ -262,14 +298,18 @@ int yama_ptrace_access_check(struct task_struct *child,
                        /* No additional restrictions. */
                        break;
                case YAMA_SCOPE_RELATIONAL:
+                       rcu_read_lock();
                        if (!task_is_descendant(current, child) &&
                            !ptracer_exception_found(current, child) &&
-                           !ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+                           !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
                                rc = -EPERM;
+                       rcu_read_unlock();
                        break;
                case YAMA_SCOPE_CAPABILITY:
-                       if (!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+                       rcu_read_lock();
+                       if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
                                rc = -EPERM;
+                       rcu_read_unlock();
                        break;
                case YAMA_SCOPE_NO_ATTACH:
                default:
@@ -307,8 +347,10 @@ int yama_ptrace_traceme(struct task_struct *parent)
        /* Only disallow PTRACE_TRACEME on more aggressive settings. */
        switch (ptrace_scope) {
        case YAMA_SCOPE_CAPABILITY:
-               if (!ns_capable(task_user_ns(parent), CAP_SYS_PTRACE))
+               rcu_read_lock();
+               if (!ns_capable(__task_cred(parent)->user_ns, CAP_SYS_PTRACE))
                        rc = -EPERM;
+               rcu_read_unlock();
                break;
        case YAMA_SCOPE_NO_ATTACH:
                rc = -EPERM;