sched: Use dl_bw_of() under RCU read lock

commit 66339c31bc3978d5fff9c4b4cb590a861def4db2 upstream.

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 <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140922183624.11015.71558.stgit@localhost
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 677ebad..e3b8502 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1895,6 +1895,8 @@ 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;
 }
 
@@ -1903,6 +1905,8 @@ 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++;
 
@@ -7458,6 +7462,8 @@ 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
@@ -7479,6 +7485,8 @@ static int sched_dl_global_constraints(void)
                        break;
        }
 
+       rcu_read_unlock();
+
        return ret;
 }
 
@@ -7494,6 +7502,7 @@ 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...
         */
@@ -7504,6 +7513,7 @@ 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)