rfkill: detect bogus double-registering (v2)

Detect and abort with -EEXIST if rfkill_register is called twice on the
same rfkill struct.  And WARN_ON(it) for good measure.

While at it, flag when we are adding the first switch of a type, we will
need that information later.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/net/rfkill/rfkill.c b/net/rfkill/rfkill.c
index 35a9994e2339..1f23de20a85e 100644
--- a/net/rfkill/rfkill.c
+++ b/net/rfkill/rfkill.c
@@ -525,17 +525,44 @@ static struct class rfkill_class = {
         .dev_uevent     = rfkill_dev_uevent,
 };
 
+static int rfkill_check_duplicity(const struct rfkill *rfkill)
+{
+        struct rfkill *p;
+        unsigned long seen[BITS_TO_LONGS(RFKILL_TYPE_MAX)];
+
+        memset(seen, 0, sizeof(seen));
+
+        list_for_each_entry(p, &rfkill_list, node) {
+                if (p == rfkill) {
+                        WARN_ON(1);
+                        return -EEXIST;
+                }
+                set_bit(p->type, seen);
+        }
+
+        /* 0: first switch of its kind */
+        return test_bit(rfkill->type, seen);
+}
+
 static int rfkill_add_switch(struct rfkill *rfkill)
 {
+        int error;
+
         mutex_lock(&rfkill_mutex);
 
+        error = rfkill_check_duplicity(rfkill);
+        if (error < 0)
+                goto unlock_out;
+
         rfkill_toggle_radio(rfkill, rfkill_states[rfkill->type], 0);
 
         list_add_tail(&rfkill->node, &rfkill_list);
 
+        error = 0;
+unlock_out:
         mutex_unlock(&rfkill_mutex);
 
-        return 0;
+        return error;
 }
 
 static void rfkill_remove_switch(struct rfkill *rfkill)