[PATCH] Input: always accept EV_SYN in input_event()

[Dmitry Torokhov]

Commit 0cd587735205 ("Input: preallocate memory to hold event values")
moved allocation of dev->vals into input_allocate_device(), which caused
input core to accumulate events reported while seeding initial device
state before input_register_device().

However, because EV_SYN is only set in dev->evbit during
input_register_device() (and some drivers also overwrite dev->evbit
directly before registration), any EV_SYN/SYN_REPORT events sent before
registration were dropped by is_event_supported(), leaving those seeded
events stuck in dev->vals until the next SYN_REPORT after registration.

Always accept EV_SYN in input_event() and input_inject_event() without
checking dev->evbit so input_sync() flushes dev->vals as intended.

Reported-by: Karlos Abel <kabel@xxxxxxxxxxxx>, 
Fixes: 0cd587735205 ("Input: preallocate memory to hold event values")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
 drivers/input/input.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 76ed9ff40584..fae508d280db 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -452,7 +452,7 @@ void input_handle_event(struct input_dev *dev,
 void input_event(struct input_dev *dev,
 		 unsigned int type, unsigned int code, int value)
 {
-	if (is_event_supported(type, dev->evbit, EV_MAX)) {
+	if (type == EV_SYN || is_event_supported(type, dev->evbit, EV_MAX)) {
 		guard(spinlock_irqsave)(&dev->event_lock);
 		input_handle_event(dev, type, code, value);
 	}
@@ -476,7 +476,7 @@ void input_inject_event(struct input_handle *handle,
 	struct input_dev *dev = handle->dev;
 	struct input_handle *grab;
 
-	if (is_event_supported(type, dev->evbit, EV_MAX)) {
+	if (type == EV_SYN || is_event_supported(type, dev->evbit, EV_MAX)) {
 		guard(spinlock_irqsave)(&dev->event_lock);
 		guard(rcu)();
 
-- 
2.56.0.385.gd3acb90ef8-goog


-- 
Dmitry