rfkill: sync before userspace visibility/changes

If userspace quickly opens /dev/rfkill after a new
instance was created, it might see the old state of
the instance from before the sync work runs and may
even _change_ the state, only to have the sync work
change it again.

Fix this by doing the sync inline where needed, not
just for /dev/rfkill but also for sysfs.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index 01fca7a..0863089 100644 (file)
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -48,6 +48,7 @@ struct rfkill {
        bool                    persistent;
        bool                    polling_paused;
        bool                    suspended;
+       bool                    need_sync;
 
        const struct rfkill_ops *ops;
        void                    *data;
@@ -368,6 +369,17 @@ static void rfkill_set_block(struct rfkill *rfkill, bool blocked)
                rfkill_event(rfkill);
 }
 
+static void rfkill_sync(struct rfkill *rfkill)
+{
+       lockdep_assert_held(&rfkill_global_mutex);
+
+       if (!rfkill->need_sync)
+               return;
+
+       rfkill_set_block(rfkill, rfkill_global_states[rfkill->type].cur);
+       rfkill->need_sync = false;
+}
+
 static void rfkill_update_global_state(enum rfkill_type type, bool blocked)
 {
        int i;
@@ -730,6 +742,10 @@ static ssize_t soft_show(struct device *dev, struct device_attribute *attr,
 {
        struct rfkill *rfkill = to_rfkill(dev);
 
+       mutex_lock(&rfkill_global_mutex);
+       rfkill_sync(rfkill);
+       mutex_unlock(&rfkill_global_mutex);
+
        return sysfs_emit(buf, "%d\n", (rfkill->state & RFKILL_BLOCK_SW) ? 1 : 0);
 }
 
@@ -751,6 +767,7 @@ static ssize_t soft_store(struct device *dev, struct device_attribute *attr,
                return -EINVAL;
 
        mutex_lock(&rfkill_global_mutex);
+       rfkill_sync(rfkill);
        rfkill_set_block(rfkill, state);
        mutex_unlock(&rfkill_global_mutex);
 
@@ -783,6 +800,10 @@ static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 {
        struct rfkill *rfkill = to_rfkill(dev);
 
+       mutex_lock(&rfkill_global_mutex);
+       rfkill_sync(rfkill);
+       mutex_unlock(&rfkill_global_mutex);
+
        return sysfs_emit(buf, "%d\n", user_state_from_blocked(rfkill->state));
 }
 
@@ -805,6 +826,7 @@ static ssize_t state_store(struct device *dev, struct device_attribute *attr,
                return -EINVAL;
 
        mutex_lock(&rfkill_global_mutex);
+       rfkill_sync(rfkill);
        rfkill_set_block(rfkill, state == RFKILL_USER_STATE_SOFT_BLOCKED);
        mutex_unlock(&rfkill_global_mutex);
 
@@ -1032,14 +1054,10 @@ static void rfkill_uevent_work(struct work_struct *work)
 
 static void rfkill_sync_work(struct work_struct *work)
 {
-       struct rfkill *rfkill;
-       bool cur;
-
-       rfkill = container_of(work, struct rfkill, sync_work);
+       struct rfkill *rfkill = container_of(work, struct rfkill, sync_work);
 
        mutex_lock(&rfkill_global_mutex);
-       cur = rfkill_global_states[rfkill->type].cur;
-       rfkill_set_block(rfkill, cur);
+       rfkill_sync(rfkill);
        mutex_unlock(&rfkill_global_mutex);
 }
 
@@ -1087,6 +1105,7 @@ int __must_check rfkill_register(struct rfkill *rfkill)
                        round_jiffies_relative(POLL_INTERVAL));
 
        if (!rfkill->persistent || rfkill_epo_lock_active) {
+               rfkill->need_sync = true;
                schedule_work(&rfkill->sync_work);
        } else {
 #ifdef CONFIG_RFKILL_INPUT
@@ -1171,6 +1190,7 @@ static int rfkill_fop_open(struct inode *inode, struct file *file)
                ev = kzalloc(sizeof(*ev), GFP_KERNEL);
                if (!ev)
                        goto free;
+               rfkill_sync(rfkill);
                rfkill_fill_event(&ev->ev, rfkill, RFKILL_OP_ADD);
                list_add_tail(&ev->list, &data->events);
        }