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

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Message-ID: <58f5cf69-3b3b-62f2-9f73-49c51176a534@gmail.com>
Date:   Sat, 6 Nov 2021 22:56:33 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Ajay Garg <ajaygargnsit@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>, jirislaby@...nel.org,
        kernel@...il.dk, David Laight <David.Laight@...lab.com>
Cc:     "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 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?



With regards,
Pavel Skripkin