rcu: Force boolean subscript for expedited stall warnings

commit ec3833ed02ae6ef2a933ece9de7cbab0c64c699e upstream.

The cpu_online() function can return values other than 0 and 1, which
can result in subscript overflow when applied to a two-element array.
This commit allows for this behavior by using "!!" on the return value
from cpu_online() when used as a subscript.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: "Rantala, Tommi" <tommi.t.rantala@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8a62cbfe1f2ff835e32bbadaff487527bd9a65a6..4e886ccd40db169a48b695f7c31d902cc07b2dd1 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3817,7 +3817,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
                                        continue;
                                rdp = per_cpu_ptr(rsp->rda, cpu);
                                pr_cont(" %d-%c%c%c", cpu,
-                                       "O."[cpu_online(cpu)],
+                                       "O."[!!cpu_online(cpu)],
                                        "o."[!!(rdp->grpmask & rnp->expmaskinit)],
                                        "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]);
                        }