FAILED: patch "[PATCH] Input: always accept EV_SYN in input_event()" failed to apply to 6.12-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x c1d13bfdb9c75c2885d10332174a887349eb0b51
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107052409-failed-6.12-c1d13bfdb9c7@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From c1d13bfdb9c75c2885d10332174a887349eb0b51 Mon Sep 17 00:00:00 2001
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: Sun, 11 Oct 2026 23:12:40 -0700
Subject: [PATCH] Input: always accept EV_SYN in input_event()

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@voidship.net>,
Fixes: 0cd587735205 ("Input: preallocate memory to hold event values")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Acked-by: Jiri Kosina <jkosina@suse.com>
Link: https://patch.msgid.link/asx50uz6iafsyAd5@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 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 1cca6d48f5977..3e6af517c596b 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -391,7 +391,7 @@ 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);
 	}
@@ -415,7 +415,7 @@ 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)();
 
-- 
2.53.0