Re: [PATCH 1/5] lib: make bitmap_parselist_user() a wrapper on bitmap_parselist()

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Yury Norov <yury.norov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
	Matthew Wilcox <willy@infradead.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	Mike Travis <travis@sgi.com>, Yury Norov <ynorov@marvell.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] lib: make bitmap_parselist_user() a wrapper on bitmap_parselist()
Date: Wed, 3 Apr 2019 14:15:22 +0300	[thread overview]
Message-ID: <20190403111522.GP9224@smile.fi.intel.com> (raw)
In-Reply-To: <20190403044540.16322-2-ynorov@marvell.com>

On Wed, Apr 03, 2019 at 07:45:36AM +0300, Yury Norov wrote:
> Currently we parse user data byte after byte which leads to
> overcomplification of parsing algorithm. The only user of
> bitmap_parselist_user() is not performance-critical, and so we
> can copy user data to kernel buffer and simply call
> bitmap_parselist(). This rework lets us unify and simplify
> bitmap_parselist() and bitmap_parselist_user(), which is done
> in the following patch.

> +	buf = kmalloc(ulen + 1, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	buf[ulen] = 0;
> +
> +	ret = copy_from_user(buf, ubuf, ulen);
> +	if (ret)
> +		goto out;

Why not memdup_user() ?

-- 
With Best Regards,
Andy Shevchenko