linux-kernel - Re: [PATCH v5 3/4] mm/page_owner: Print memcg information

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Date:   Tue, 8 Feb 2022 16:15:05 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Ira Weiny <ira.weiny@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <guro@...com>,
        Rafael Aquini <aquini@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH v5 3/4] mm/page_owner: Print memcg information

On Tue 08-02-22 13:13:15, Michal Hocko wrote:
> On Mon 07-02-22 19:05:31, Waiman Long wrote:
[...]
> > +	ret += scnprintf(kbuf + ret, count - ret, "\n");
> 
> I do not see any overflow prevention here. I believe you really need to
> check ret >= count after each scnprintf/cgroup_name.

OK, I have only now realized that scnprintf would return size - 1 on
overflow so explicitly checking for the overlow shouldn't be reallu
necessary.
-- 
Michal Hocko
SUSE Labs