CRED: Use RCU to access another task's creds and to release a task's own creds
Use RCU to access another task's creds and to release a task's own creds.
This means that it will be possible for the credentials of a task to be
replaced without another task (a) requiring a full lock to read them, and (b)
seeing deallocated memory.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 10715d1..c863036 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -95,13 +95,18 @@
static int task_has_security(struct task_struct *tsk,
u32 perms)
{
- struct task_security_struct *tsec;
+ const struct task_security_struct *tsec;
+ u32 sid = 0;
- tsec = tsk->cred->security;
+ rcu_read_lock();
+ tsec = __task_cred(tsk)->security;
+ if (tsec)
+ sid = tsec->sid;
+ rcu_read_unlock();
if (!tsec)
return -EACCES;
- return avc_has_perm(tsec->sid, SECINITSID_SECURITY,
+ return avc_has_perm(sid, SECINITSID_SECURITY,
SECCLASS_SECURITY, perms, NULL);
}