Input: do not pass injected events back to the originating handler

Sometimes input handlers (as opposed to input devices) have a need to
inject (or re-inject) events back into input core. For example sysrq
filter may want to inject previously suppressed Alt-SysRq so that user
can take a screen print. In this case we do not want to pass such events
back to the same same handler that injected them to avoid loops.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 26 insertions, 11 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 75bed635b98d..7f26ca6ecf75 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -74,6 +74,7 @@ static int input_defuzz_abs_event(int value, int old_val, int fuzz)
  * dev->event_lock held and interrupts disabled.
  */
 static void input_pass_event(struct input_dev *dev,
+                             struct input_handler *src_handler,
                              unsigned int type, unsigned int code, int value)
 {
         struct input_handler *handler;
@@ -92,6 +93,15 @@ static void input_pass_event(struct input_dev *dev,
                                 continue;
 
                         handler = handle->handler;
+
+                        /*
+                         * If this is the handler that injected this
+                         * particular event we want to skip it to avoid
+                         * filters firing again and again.
+                         */
+                        if (handler == src_handler)
+                                continue;
+
                         if (!handler->filter) {
                                 if (filtered)
                                         break;
@@ -121,7 +131,7 @@ static void input_repeat_key(unsigned long data)
         if (test_bit(dev->repeat_key, dev->key) &&
             is_event_supported(dev->repeat_key, dev->keybit, KEY_MAX)) {
 
-                input_pass_event(dev, EV_KEY, dev->repeat_key, 2);
+                input_pass_event(dev, NULL, EV_KEY, dev->repeat_key, 2);
 
                 if (dev->sync) {
                         /*
@@ -130,7 +140,7 @@ static void input_repeat_key(unsigned long data)
                          * Otherwise assume that the driver will send
                          * SYN_REPORT once it's done.
                          */
-                        input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+                        input_pass_event(dev, NULL, EV_SYN, SYN_REPORT, 1);
                 }
 
                 if (dev->rep[REP_PERIOD])
@@ -163,6 +173,7 @@ static void input_stop_autorepeat(struct input_dev *dev)
 #define INPUT_PASS_TO_ALL       (INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)
 
 static int input_handle_abs_event(struct input_dev *dev,
+                                  struct input_handler *src_handler,
                                   unsigned int code, int *pval)
 {
         bool is_mt_event;
@@ -206,13 +217,15 @@ static int input_handle_abs_event(struct input_dev *dev,
         /* Flush pending "slot" event */
         if (is_mt_event && dev->slot != input_abs_get_val(dev, ABS_MT_SLOT)) {
                 input_abs_set_val(dev, ABS_MT_SLOT, dev->slot);
-                input_pass_event(dev, EV_ABS, ABS_MT_SLOT, dev->slot);
+                input_pass_event(dev, src_handler,
+                                 EV_ABS, ABS_MT_SLOT, dev->slot);
         }
 
         return INPUT_PASS_TO_HANDLERS;
 }
 
 static void input_handle_event(struct input_dev *dev,
+                               struct input_handler *src_handler,
                                unsigned int type, unsigned int code, int value)
 {
         int disposition = INPUT_IGNORE_EVENT;
@@ -265,7 +278,8 @@ static void input_handle_event(struct input_dev *dev,
 
         case EV_ABS:
                 if (is_event_supported(code, dev->absbit, ABS_MAX))
-                        disposition = input_handle_abs_event(dev, code, &value);
+                        disposition = input_handle_abs_event(dev, src_handler,
+                                                             code, &value);
 
                 break;
 
@@ -323,7 +337,7 @@ static void input_handle_event(struct input_dev *dev,
                 dev->event(dev, type, code, value);
 
         if (disposition & INPUT_PASS_TO_HANDLERS)
-                input_pass_event(dev, type, code, value);
+                input_pass_event(dev, src_handler, type, code, value);
 }
 
 /**
@@ -352,7 +366,7 @@ void input_event(struct input_dev *dev,
 
                 spin_lock_irqsave(&dev->event_lock, flags);
                 add_input_randomness(type, code, value);
-                input_handle_event(dev, type, code, value);
+                input_handle_event(dev, NULL, type, code, value);
                 spin_unlock_irqrestore(&dev->event_lock, flags);
         }
 }
@@ -382,7 +396,8 @@ void input_inject_event(struct input_handle *handle,
                 rcu_read_lock();
                 grab = rcu_dereference(dev->grab);
                 if (!grab || grab == handle)
-                        input_handle_event(dev, type, code, value);
+                        input_handle_event(dev, handle->handler,
+                                           type, code, value);
                 rcu_read_unlock();
 
                 spin_unlock_irqrestore(&dev->event_lock, flags);
@@ -595,10 +610,10 @@ static void input_dev_release_keys(struct input_dev *dev)
                 for (code = 0; code <= KEY_MAX; code++) {
                         if (is_event_supported(code, dev->keybit, KEY_MAX) &&
                             __test_and_clear_bit(code, dev->key)) {
-                                input_pass_event(dev, EV_KEY, code, 0);
+                                input_pass_event(dev, NULL, EV_KEY, code, 0);
                         }
                 }
-                input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+                input_pass_event(dev, NULL, EV_SYN, SYN_REPORT, 1);
         }
 }
 
@@ -873,9 +888,9 @@ int input_set_keycode(struct input_dev *dev,
             !is_event_supported(old_keycode, dev->keybit, KEY_MAX) &&
             __test_and_clear_bit(old_keycode, dev->key)) {
 
-                input_pass_event(dev, EV_KEY, old_keycode, 0);
+                input_pass_event(dev, NULL, EV_KEY, old_keycode, 0);
                 if (dev->sync)
-                        input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+                        input_pass_event(dev, NULL, EV_SYN, SYN_REPORT, 1);
         }
 
  out: