linux-kernel - Re: [PATCH 6/6] exec: open code copy_string

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Date:   Mon, 6 Apr 2020 05:10:32 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jeremy Kerr <jk@...abs.org>, Arnd Bergmann <arnd@...db.de>,
        linuxppc-dev@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] exec: open code copy_string_kernel

On Mon, Apr 06, 2020 at 02:03:12PM +0200, Christoph Hellwig wrote:
> +	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating null */;

If you end up doing another version of this, it's a terminating NUL, not null.

I almost wonder if we shouldn't have

#define TERMINATING_NUL		1

in kernel.h.

	int len = strnlen(arg, MAX_ARG_STRLEN) + TERMINATING_NUL;

has a certain appeal.  There's the risk people might misuse it though ...

	str[end] = TERMINATING_NUL;

so probably not a good idea.