From: "Paul E. McKenney" <paulmck@xxxxxxxxxx> [ Upstream commit ab2756ea6b74987849b44ad0e33c3cfec159033b ] If the cpu_possible_mask is sparse (for example, if bits are set only for CPUs 0, 4, 8, ...), then rcu_tasks_invoke_cbs() will access per-CPU data for a CPU not in cpu_possible_mask. It makes these accesses while doing a workqueue-based binary search for non-empty callback lists. Although this search must pass through CPUs not represented in cpu_possible_mask, it has no need to check the callback list for such CPUs. This commit therefore changes the rcu_tasks_invoke_cbs() function's binary search so as to only check callback lists for CPUs present in cpu_possible_mask. Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/rcu/tasks.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 30c42797f53b..1664e472524b 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -460,7 +460,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu } } - if (rcu_segcblist_empty(&rtpcp->cblist)) + if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu)) return; raw_spin_lock_irqsave_rcu_node(rtpcp, flags); rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq)); -- 2.35.1
