diff options
author | Paul E. McKenney <paulmck@kernel.org> | 2019-11-04 08:22:45 -0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-11 04:35:08 -0800 |
commit | 6a4fea54ab46c2623d74449eaaff8a7e08b19c5e (patch) | |
tree | 51fcb4f62c24e094ff3fffca0e4806557eb9fe2a /kernel | |
parent | c71706a5ffff80c580f91ee683ce3ebfc79c2998 (diff) |
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>
Diffstat (limited to 'kernel')
-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 && |