linux-kernel - Re: [RESEND PATCH] Input: elantech - Fix stack out of bound access in elantech_change_report

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Date:   Tue, 16 Nov 2021 10:53:09 +0100
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Phoenix Huang <phoenix@....com.tw>, jingle.wu@....com.tw,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] Input: elantech - Fix stack out of bound access
 in elantech_change_report_id()

On Tue, Nov 16, 2021 at 09:32:34AM +0100, Wolfram Sang wrote:
> On Tue, Nov 16, 2021 at 08:22:23AM +0100, Andrea Righi wrote:
> > The array param[] in elantech_change_report_id() must be at least 3
> > bytes, because elantech_read_reg_params() is calling ps2_command() with
> > PSMOUSE_CMD_GETINFO, that is going to access 3 bytes from param[], but
> > it's defined in the stack as an array of 2 bytes, therefore we have a
> > potential stack out-of-bounds access here, also confirmed by KASAN:
> 
> I think a comment in the code why the array size is 3 when only 2 values
> are defined would be helpful. Like a short summary of the above.
> 

Good idea, I like it, I'll send a v2 adding such comment.

Thanks!
-Andrea