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

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Date:   Tue, 16 Apr 2019 16:08:38 +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>,
        Guenter Roeck <linux@...ck-us.net>,
        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 Mon, Apr 15, 2019 at 11:37:57PM -0700, Yury Norov wrote:
> From: Yury Norov <ynorov@...vell.com>
> 
> 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 duplicate 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.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> 
> Signed-off-by: Yury Norov <ynorov@...vell.com>
> ---
>  lib/bitmap.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 3f3b8051f342..c63ddd06a5da 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -632,19 +632,22 @@ EXPORT_SYMBOL(bitmap_parselist);
>   * @nmaskbits: size of bitmap, in bits.
>   *
>   * Wrapper for bitmap_parselist(), providing it with user buffer.
> - *
> - * We cannot have this as an inline function in bitmap.h because it needs
> - * linux/uaccess.h to get the access_ok() declaration and this causes
> - * cyclic dependencies.
>   */
>  int bitmap_parselist_user(const char __user *ubuf,
>  			unsigned int ulen, unsigned long *maskp,
>  			int nmaskbits)
>  {
> -	if (!access_ok(ubuf, ulen))
> -		return -EFAULT;
> -	return __bitmap_parselist((const char __force *)ubuf,
> -					ulen, 1, maskp, nmaskbits);
> +	char *buf;
> +	int ret;
> +
> +	buf = memdup_user_nul(ubuf, ulen);
> +	if (IS_ERR(buf))
> +		return PTR_ERR(buf);
> +
> +	ret = bitmap_parselist(buf, maskp, nmaskbits);
> +
> +	kfree(buf);
> +	return ret;
>  }
>  EXPORT_SYMBOL(bitmap_parselist_user);
>  
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko