[PATCH (resend)] Input: MT - limit max slots

Tetsuo Handa
2024-07-29T12:51:52Z

syzbot is reporting too large allocation at input_mt_init_slots(), for
num_slots is supplied from userspace using ioctl(UI_DEV_CREATE).

Since nobody knows possible max slots, this patch chose 1024.

Reported-by: syzbot <syzbot+0122fa359a69694395d5@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=0122fa359a69694395d5
Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
This patch was tested in linux-next between next-20240611 and next-20240729
via my tree. Who can take this patch? If nobody can, I will send to Linus.

drivers/input/input-mt.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index 14b53dac1253..6b04a674f832 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -46,6 +46,9 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots,
return 0;
if (mt)
return mt->num_slots != num_slots ? -EINVAL : 0;
+ /* Arbitrary limit for avoiding too large memory allocation. */
+ if (num_slots > 1024)
+ return -EINVAL;

mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
if (!mt)
--
2.43.5