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

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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>
This commit is contained in:
Oleg Nesterov 2013-12-23 17:45:01 -05:00 committed by Paul Moore
parent 46d01d6322
commit c0c1439541
1 changed files with 2 additions and 2 deletions
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4
security/selinux/hooks.c
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@ -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,