# Re: \[PATCH\] HID: wacom: Correct NULL dereference on AES pen proximity

- From: Jiri Kosina \<jikos@kernel.org\>
- Date: 2021-01-26 10:57:05 
- List: linux-input
- Page: https://ratatoskr.run/linux-input/2021/01/6871146
- Thread: https://ratatoskr.run/linux-input/2021/01/6870965/t.md

```text
On Thu, 21 Jan 2021, Jason Gerecke wrote:

> The recent commit to fix a memory leak introduced an inadvertant NULL
> pointer dereference. The `wacom_wac->pen_fifo` variable was never
> intialized, resuling in a crash whenever functions tried to use it.
> Since the FIFO is only used by AES pens (to buffer events from pen
> proximity until the hardware reports the pen serial number) this would
> have been easily overlooked without testing an AES device.
> 
> This patch converts `wacom_wac->pen_fifo` over to a pointer (since the
> call to `devres_alloc` allocates memory for us) and ensures that we assign
> it to point to the allocated and initalized `pen_fifo` before the function
> returns.
> 
> Link: https://github.com/linuxwacom/input-wacom/issues/230
> Fixes: 37309f47e2f5 ("HID: wacom: Fix memory leakage caused by kfifo_alloc")
> CC: <redacted> # v4.19+
> Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
> Tested-by: Ping Cheng <ping.cheng@wacom.com>

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs

```