Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 19 Sep 2019 22:56:15 -0400 (EDT)
From:   Nicolas Pitre <nico@fluxnic.net>
To:     Greg KH <gregkh@linuxfoundation.org>
cc:     Xiaoming Ni <nixiaoming@huawei.com>, penberg@cs.helsinki.fi,
        jslaby@suse.com, textshell@uchuujin.de, sam@ravnborg.org,
        daniel.vetter@ffwll.ch, mpatocka@redhat.com, ghalat@redhat.com,
        linux-kernel@vger.kernel.org, yangyingliang@huawei.com,
        yuehaibing@huawei.com, zengweilin@huawei.com
Subject: Re: [PATCH] tty:vt: Add check the return value of kzalloc to avoid
 oops
In-Reply-To: <20190919092933.GA2684163@kroah.com>
Message-ID: <nycvar.YSQ.7.76.1909192251210.24536@knanqh.ubzr>
References: <1568884695-56789-1-git-send-email-nixiaoming@huawei.com> <20190919092933.GA2684163@kroah.com>
User-Agent: Alpine 2.21 (LFD 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, 19 Sep 2019, Greg KH wrote:

> On Thu, Sep 19, 2019 at 05:18:15PM +0800, Xiaoming Ni wrote:
> > Using kzalloc() to allocate memory in function con_init(), but not
> > checking the return value, there is a risk of null pointer references
> > oops.
> > 
> > Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
> 
> We keep having this be "reported" :(

Something probably needs to be "communicated" about that.

> >  		vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), GFP_NOWAIT);
> > +		if (unlikely(!vc)) {
> > +			pr_warn("%s:failed to allocate memory for the %u vc\n",
> > +					__func__, currcons);
> > +			break;
> > +		}
> 
> At init, this really can not happen.  Have you see it ever happen?

This is maybe too subtle a fact. The "communication" could be done with 
some GFP_WONTFAIL flag, and have the allocator simply pannic() if it 
ever fails.


Nicolas