Commit c0c14395 authored Dec 23, 2013 by Oleg Nesterov Committed by Paul Moore Dec 23, 2013

selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock()



selinux_setprocattr() does ptrace_parent(p) under task_lock(p),
but task_struct->alloc_lock doesn't pin ->parent or ->ptrace,
this looks confusing and triggers the "suspicious RCU usage"
warning because ptrace_parent() does rcu_dereference_check().

And in theory this is wrong, spin_lock()->preempt_disable()
doesn't necessarily imply rcu_read_lock() we need to access
the ->parent.

Reported-by: Evan McNabb <emcnabb@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>

parent 46d01d63

security/selinux/hooks.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -5588,11 +5588,11 @@ static int selinux_setprocattr(struct task_struct *p,
		/* Check for ptracing, and update the task SID if ok.
		Otherwise, leave SID unchanged and fail. */
		ptsid = 0;
		task_lock(p);
		rcu_read_lock();
		tracer = ptrace_parent(p);
		if (tracer)
		ptsid = task_sid(tracer);
		task_unlock(p);
		rcu_read_unlock();

		if (tracer) {
		error = avc_has_perm(ptsid, sid, SECCLASS_PROCESS,

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