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[195.135.220.15]) by mx.google.com with ESMTPS id b89si993438edf.309.2019.04.18.06.03.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 06:03:12 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 25228B64C; Thu, 18 Apr 2019 13:03:12 +0000 (UTC) Date: Thu, 18 Apr 2019 15:03:10 +0200 From: Michal Hocko To: Laurent Dufour Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yang Shi , Michal Koutny Subject: Re: [PATCH] mm: use mm.arg_lock in get_cmdline() Message-ID: <20190418130310.GJ6567@dhcp22.suse.cz> References: <20190418125827.57479-1-ldufour@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190418125827.57479-1-ldufour@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Michal has posted the same patch few days ago http://lkml.kernel.org/r/20190417120347.15397-1-mkoutny@suse.com On Thu 18-04-19 14:58:27, Laurent Dufour wrote: > The commit 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end > and env_start|end in mm_struct") introduce the spinlock arg_lock to protect > the arg_* and env_* field of the mm_struct structure. > > While reading the code, I found that this new spinlock was not used in > get_cmdline() to protect access to these fields. > > Fixing this even if there is no issue reported yet for this. > > Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct") > Cc: Yang Shi > Signed-off-by: Laurent Dufour > --- > mm/util.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/util.c b/mm/util.c > index 05a464929b3e..789760c3028b 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen) > if (!mm->arg_end) > goto out_mm; /* Shh! No looking before we're done */ > > - down_read(&mm->mmap_sem); > + spin_lock(&mm->arg_lock); > arg_start = mm->arg_start; > arg_end = mm->arg_end; > env_start = mm->env_start; > env_end = mm->env_end; > - up_read(&mm->mmap_sem); > + spin_unlock(&mm->arg_lock); > > len = arg_end - arg_start; > > -- > 2.21.0 -- Michal Hocko SUSE Labs