linux-kernel - Re: [PATCH] tty: vt: keyboard: do not copy an extra-byte in copy_to

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Message-ID: <CAHP4M8VXpGha1gs9GrY5JGFXLOCWHFMS7ZHbeDFQz0DW14TQ7A@mail.gmail.com>
Date:   Sun, 7 Nov 2021 01:37:31 +0530
From:   Ajay Garg <ajaygargnsit@...il.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>, jirislaby@...nel.org,
        kernel@...il.dk, David Laight <David.Laight@...lab.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tty: vt: keyboard: do not copy an extra-byte in copy_to_user

On Sun, Nov 7, 2021 at 1:26 AM Pavel Skripkin <paskripkin@...il.com> wrote:
>
> On 11/6/21 22:20, Ajay Garg wrote:
> > I vote for David's strscpy "fix", as it is simple, and does away with
> > the dependency on the length of "func_table[kb_func]".
> >
>
> strscpy fix sounds reasonable to me. just to be save in future.
>
> There is only one thing I am wondering about: translation table entries
> are set by user using this struct
>
> struct kbsentry {
>         unsigned char kb_func;
>         unsigned char kb_string[512];
> };
>
> it means entries cannot be longer than sizeof(kbsentry::kb_string) - 1
> at all. Do we need extra branching with strscpy() or do we need to do
> anything else here?

Hi Pavel,

Please see my latest comments in the last reply.


>
>
>
> With regards,
> Pavel Skripkin