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| author | Paul E. McKenney <paulmck@kernel.org> | 2019-11-04 08:22:45 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-11 04:36:40 -0800 |
| commit | 09d89628a6d711d3887bdc599b556081443a4dd9 (patch) | |
| tree | 191c5b129da601601d543449578679ef7d01386b | |
| parent | 35e80e1ecf8c7af1c2457d0f067a6b2a4ac2bc67 (diff) | |
| download | linux-rt-09d89628a6d711d3887bdc599b556081443a4dd9.tar.gz | |
rcu: Use READ_ONCE() for ->expmask in rcu_read_unlock_special()
commit c51f83c315c392d9776c33eb16a2fe1349d65c7f upstream.
The rcu_node structure's ->expmask field is updated only when holding the
->lock, but is also accessed locklessly. This means that all ->expmask
updates must use WRITE_ONCE() and all reads carried out without holding
->lock must use READ_ONCE(). This commit therefore changes the lockless
->expmask read in rcu_read_unlock_special() to use READ_ONCE().
Reported-by: syzbot+99f4ddade3c22ab0cf23@syzkaller.appspotmail.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 270779418a60..f849e7429816 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -612,7 +612,7 @@ static void rcu_read_unlock_special(struct task_struct *t) t->rcu_read_unlock_special.b.exp_hint = false; exp = (t->rcu_blocked_node && t->rcu_blocked_node->exp_tasks) || - (rdp->grpmask & rnp->expmask) || + (rdp->grpmask & READ_ONCE(rnp->expmask)) || tick_nohz_full_cpu(rdp->cpu); // Need to defer quiescent state until everything is enabled. if (irqs_were_disabled && use_softirq && |