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Date:   Thu, 2 Jun 2022 15:25:14 -0700
From:   Roman Gushchin <roman.gushchin@linux.dev>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, Dave Chinner <dchinner@redhat.com>,
        linux-kernel@vger.kernel.org,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Hillf Danton <hdanton@sina.com>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Muchun Song <songmuchun@bytedance.com>
Subject: Re: [PATCH v5 6/6] mm: shrinkers: add scan interface for shrinker
 debugfs
Message-ID: <Ypk4yuvJQ1ObIEJH@carbon>
References: <20220601032227.4076670-1-roman.gushchin@linux.dev>
 <20220601032227.4076670-7-roman.gushchin@linux.dev>
 <20220601142351.5e04fea5586ca51898d8785f@linux-foundation.org>
 <YpgKttTowT22mKPQ@carbon>
 <20220602114132.f6e5675b2d2a4085b9b1e8c4@linux-foundation.org>
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On Thu, Jun 02, 2022 at 11:41:32AM -0700, Andrew Morton wrote:
> On Wed, 1 Jun 2022 17:56:22 -0700 Roman Gushchin <roman.gushchin@linux.dev> wrote:
> 
> > > 
> > > > +	ssize_t ret;
> > > > +
> > > > +	if (copy_from_user(kbuf, buf, read_len))
> > > > +		return -EFAULT;
> > > > +	kbuf[read_len] = '\0';
> > > > +
> > > > +	if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2)
> > > 
> > > Was it intentional to permit more than three args?
> > 
> > Good catch! No, of course it wasn't intentional.
> > 
> > Below is an updated version of this patch.
> > 
> > ...
> >
> > +	if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) != 2)
> > +		return -EINVAL;
> 
> s/2/3/methinks?
> 
> 

My bad, of course. Thanks!

--

diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index 12026472daae..e5b40c43221d 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -124,7 +124,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
                return -EFAULT;
        kbuf[read_len] = '\0';
 
-       if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) != 2)
+       if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) != 3)
                return -EINVAL;
 
        if (nid < 0 || nid >= nr_node_ids)