[PATCH] Input: MT - use __GFP_NOWARN allocation at input_mt_init_slots()

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

syzbot is reporting too large allocation at input_mt_init_slots() {1], for
num_slots is supplied from userspace using ioctl(UI_DEV_CREATE).
Also, replace n2 with array_size(), for 32bits variable n2 will overflow
if num_slots >= 65536.

Link: https://syzkaller.appspot.com/bug?extid=0122fa359a69694395d5 [1]
Reported-by: syzbot <syzbot+0122fa359a69694395d5@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/input/input-mt.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index 14b53dac1253..cf74579462ba 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -47,7 +47,7 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots,
 	if (mt)
 		return mt->num_slots != num_slots ? -EINVAL : 0;
 
-	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
+	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL | __GFP_NOWARN);
 	if (!mt)
 		goto err_mem;
 
@@ -80,8 +80,8 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots,
 	if (flags & INPUT_MT_SEMI_MT)
 		__set_bit(INPUT_PROP_SEMI_MT, dev->propbit);
 	if (flags & INPUT_MT_TRACK) {
-		unsigned int n2 = num_slots * num_slots;
-		mt->red = kcalloc(n2, sizeof(*mt->red), GFP_KERNEL);
+		mt->red = kcalloc(array_size(num_slots, num_slots),
+				  sizeof(*mt->red), GFP_KERNEL | __GFP_NOWARN);
 		if (!mt->red)
 			goto err_mem;
 	}
-- 
2.34.1