From: Claudia Pellegrino Date: Sun, 14 Nov 2021 02:53:27 +0000 (+0100) Subject: HID: magicmouse: prevent division by 0 on scroll X-Git-Tag: v6.1-rc5~2290^2~31 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a1091118e0d6d84c2fdb94e6c397ac790bfb9dd6;p=platform%2Fkernel%2Flinux-starfive.git HID: magicmouse: prevent division by 0 on scroll In hid_magicmouse, if the user has set scroll_speed to a value between 55 and 63 and scrolls seven times in quick succession, the step_hr variable in the magicmouse_emit_touch function becomes 0. That causes a division by zero further down in the function when it does `step_x_hr /= step_hr`. To reproduce, create `/etc/modprobe.d/hid_magicmouse.conf` with the following content: ``` options hid_magicmouse scroll_acceleration=1 scroll_speed=55 ``` Then reboot, connect a Magic Mouse and scroll seven times quickly. The system will freeze for a minute, and after that `dmesg` will confirm that a division by zero occurred. Enforce a minimum of 1 for the variable so the high resolution step count can never reach 0 even at maximum scroll acceleration. Fixes: d4b9f10a0eb6 ("HID: magicmouse: enable high-resolution scroll") Signed-off-by: Claudia Pellegrino Tested-by: José Expósito Signed-off-by: Jiri Kosina --- diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c index 686788e..d7687ce 100644 --- a/drivers/hid/hid-magicmouse.c +++ b/drivers/hid/hid-magicmouse.c @@ -256,8 +256,11 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda unsigned long now = jiffies; int step_x = msc->touches[id].scroll_x - x; int step_y = msc->touches[id].scroll_y - y; - int step_hr = ((64 - (int)scroll_speed) * msc->scroll_accel) / - SCROLL_HR_STEPS; + int step_hr = + max_t(int, + ((64 - (int)scroll_speed) * msc->scroll_accel) / + SCROLL_HR_STEPS, + 1); int step_x_hr = msc->touches[id].scroll_x_hr - x; int step_y_hr = msc->touches[id].scroll_y_hr - y;