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Yama: add RCU to drop read locking 

Stop using spinlocks in the read path. Add RCU list to handle the readers.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
Kees Cook 2012-10-18 14:53:58 -07:00
parent b566650270
commit 93b69d437e
1 changed files with 24 additions and 23 deletions
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47
security/yama/yama_lsm.c
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@ -30,6 +30,7 @@ struct ptrace_relation {
struct task_struct *tracer;
struct task_struct *tracee;
struct list_head node;
struct rcu_head rcu;
};
static LIST_HEAD(ptracer_relations);
@ -48,32 +49,31 @@ 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;
added->tracee = tracee;
added->tracer = tracer;
spin_lock_bh(&ptracer_relations_lock);
list_for_each_entry(entry, &ptracer_relations, node)
if (entry->tracee == tracee) {
relation = entry;
break;
rcu_read_lock();
list_for_each_entry_rcu(relation, &ptracer_relations, node) {
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;
list_add_rcu(&added->node, &ptracer_relations);
out:
rcu_read_unlock();
spin_unlock_bh(&ptracer_relations_lock);
if (added != relation)
kfree(added);
return rc;
return 0;
}
/**
@ -84,15 +84,18 @@ 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;
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->tracee == tracee ||
(tracer && relation->tracer == tracer)) {
list_del(&relation->node);
kfree(relation);
list_del_rcu(&relation->node);
kfree_rcu(relation, rcu);
}
}
rcu_read_unlock();
spin_unlock_bh(&ptracer_relations_lock);
}
@ -217,11 +220,10 @@ 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->tracee == tracee) {
parent = relation->tracer;
found = true;
@ -231,7 +233,6 @@ static int ptracer_exception_found(struct task_struct *tracer,
if (found && (parent == NULL || task_is_descendant(parent, tracer)))
rc = 1;
rcu_read_unlock();
spin_unlock_bh(&ptracer_relations_lock);
return rc;
}