linux-kernel - Re: [PATCH 02/18] vchecker: introduce the valid access checker

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Message-ID: <20171129053637.GA8125@js1304-P5Q-DELUXE>
Date:   Wed, 29 Nov 2017 14:36:37 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Namhyung Kim <namhyung@...nel.org>,
        Wengang Wang <wen.gang.wang@...cle.com>
Subject: Re: [PATCH 02/18] vchecker: introduce the valid access checker

On Tue, Nov 28, 2017 at 11:41:08AM -0800, Andi Kleen wrote:
> js1304@...il.com writes:
> 
> > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> Looks useful. Essentially unlimited hardware break points, combined
> with slab.

Thanks!!!

> 
> Didn't do a full review, but noticed some things below.
> > +
> > +	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
> > +	if (!buf)
> > +		return -ENOMEM;
> > +
> > +	if (copy_from_user(buf, ubuf, cnt)) {
> > +		kfree(buf);
> > +		return -EFAULT;
> > +	}
> > +
> > +	if (isspace(buf[0]))
> > +		remove = true;
> 
> and that may be uninitialized.

I will add 'cnt == 0' check above.

> and the space changes the operation? That's a strange syntax.

Intention is to clear the all the previous configuration when user
input is '\n'. Will fix it by checking '\n' directly.

> 
> > +	buf[cnt - 1] = '\0';
> 
> That's an underflow of one byte if cnt is 0.

Will add 'cnt == 0' check above.

String parsing part in this patchset will not work properly when the
last input character is not '\n'. I will fix it on the next spin.

Thanks.