Yama: higher restrictions should block PTRACE_TRACEME

[firefly-linux-kernel-4.4.55.git] / security / yama / yama_lsm.c

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 83554ee8a587fbf27bdc7095fa8a600b82aada57..d51b7c76c37da3e60ab23e7b47c2fe03249b4707 100644 (file)
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -290,10 +290,51 @@ static int yama_ptrace_access_check(struct task_struct *child,
        return rc;
 }
 
+/**
+ * yama_ptrace_traceme - validate PTRACE_TRACEME calls
+ * @parent: task that will become the ptracer of the current task
+ *
+ * Returns 0 if following the ptrace is allowed, -ve on error.
+ */
+static int yama_ptrace_traceme(struct task_struct *parent)
+{
+       int rc;
+
+       /* If standard caps disallows it, so does Yama.  We should
+        * only tighten restrictions further.
+        */
+       rc = cap_ptrace_traceme(parent);
+       if (rc)
+               return rc;
+
+       /* 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))
+                       rc = -EPERM;
+               break;
+       case YAMA_SCOPE_NO_ATTACH:
+               rc = -EPERM;
+               break;
+       }
+
+       if (rc) {
+               char name[sizeof(current->comm)];
+               printk_ratelimited(KERN_NOTICE
+                       "ptraceme of pid %d was attempted by: %s (pid %d)\n",
+                       current->pid,
+                       get_task_comm(name, parent),
+                       parent->pid);
+       }
+
+       return rc;
+}
+
 static struct security_operations yama_ops = {
        .name =                 "yama",
 
        .ptrace_access_check =  yama_ptrace_access_check,
+       .ptrace_traceme =       yama_ptrace_traceme,
        .task_prctl =           yama_task_prctl,
        .task_free =            yama_task_free,
 };