On Saturday, December 14, 2013 05:33:17 PM Oleg Nesterov wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> ---
> security/selinux/hooks.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
Applied, thanks.
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5503,11 +5503,11 @@ static int selinux_setprocattr(struct ta
> /* 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,
--
paul moore
www.paul-moore.com
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