a1091118e0
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 <linux@cpellegrino.de>
Tested-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.