[PATCH v3 3/6] sched: Use dl_bw_of() under RCU read lock

[Kirill Tkhai]

From: Kirill Tkhai <ktk...@parallels.com>

dl_bw_of() dereferences rq->rd which has to have RCU read lock held.
Probability of use-after-free isn't zero here.

Also add lockdep assert into dl_bw_cpus().

Signed-off-by: Kirill Tkhai <ktk...@parallels.com>
Cc: <sta...@vger.kernel.org> # v3.14+
---
 kernel/sched/core.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5b864e9..a300fce 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1989,6 +1989,8 @@ unsigned long to_ratio(u64 period, u64 runtime)
 #ifdef CONFIG_SMP
 inline struct dl_bw *dl_bw_of(int i)
 {
+       rcu_lockdep_assert(rcu_read_lock_sched_held(),
+                          "sched RCU must be held");
        return &cpu_rq(i)->rd->dl_bw;
 }
 
@@ -1997,6 +1999,8 @@ static inline int dl_bw_cpus(int i)
        struct root_domain *rd = cpu_rq(i)->rd;
        int cpus = 0;
 
+       rcu_lockdep_assert(rcu_read_lock_sched_held(),
+                          "sched RCU must be held");
        for_each_cpu_and(i, rd->span, cpu_active_mask)
                cpus++;
 
@@ -7623,6 +7627,8 @@ static int sched_dl_global_constraints(void)
        int cpu, ret = 0;
        unsigned long flags;
 
+       rcu_read_lock();
+
        /*
         * Here we want to check the bandwidth not being set to some
         * value smaller than the currently allocated bandwidth in
@@ -7644,6 +7650,8 @@ static int sched_dl_global_constraints(void)
                        break;
        }
 
+       rcu_read_unlock();
+
        return ret;
 }
 
@@ -7659,6 +7667,7 @@ static void sched_dl_do_global(void)
        if (global_rt_runtime() != RUNTIME_INF)
                new_bw = to_ratio(global_rt_period(), global_rt_runtime());
 
+       rcu_read_lock();
        /*
         * FIXME: As above...
         */
@@ -7669,6 +7678,7 @@ static void sched_dl_do_global(void)
                dl_b->bw = new_bw;
                raw_spin_unlock_irqrestore(&dl_b->lock, flags);
        }
+       rcu_read_unlock();
 }
 
 static int sched_rt_global_validate(void)

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