linux-kernel - Re: [PATCH 1/5] lib: make bitmap_parselist_user() a wrapper on bitmap

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Message-ID: <20190403111745.GQ9224@smile.fi.intel.com>
Date:   Wed, 3 Apr 2019 14:17:45 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Mike Travis <travis@....com>, Yury Norov <ynorov@...vell.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] lib: make bitmap_parselist_user() a wrapper on
 bitmap_parselist()

On Wed, Apr 03, 2019 at 02:15:22PM +0300, Andy Shevchenko wrote:
> 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() ?

Even more precisely (for strings) strndup_user().

-- 
With Best Regards,
Andy Shevchenko