netdev - Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg

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Message-ID: <20180427191430-mutt-send-email-mst@kernel.org>
Date:   Fri, 27 Apr 2018 19:15:30 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Kevin Easton <kevin@...rana.org>, Jason Wang <jasowang@...hat.com>,
        KVM list <kvm@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node

On Fri, Apr 27, 2018 at 06:11:31PM +0200, Dmitry Vyukov wrote:
> On Fri, Apr 27, 2018 at 6:05 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
> > On Fri, Apr 27, 2018 at 11:45:02AM -0400, Kevin Easton wrote:
> >> The struct vhost_msg within struct vhost_msg_node is copied to userspace,
> >> so it should be allocated with kzalloc() to ensure all structure padding
> >> is zeroed.
> >>
> >> Signed-off-by: Kevin Easton <kevin@...rana.org>
> >> Reported-by: syzbot+87cfa083e727a224754b@...kaller.appspotmail.com
> >
> > Does it help if a patch naming the padding is applied,
> > and then we init just the relevant field?
> > Just curious.
> 
> Yes, it would help.

I think it's slightly better that way then. node has a lot of internal
stuff we don't care to init. Would you mind taking my patch and building
on top of that then?

> >> ---
> >>  drivers/vhost/vhost.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> >> index f3bd8e9..1b84dcff 100644
> >> --- a/drivers/vhost/vhost.c
> >> +++ b/drivers/vhost/vhost.c
> >> @@ -2339,7 +2339,7 @@ EXPORT_SYMBOL_GPL(vhost_disable_notify);
> >>  /* Create a new message. */
> >>  struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
> >>  {
> >> -     struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
> >> +     struct vhost_msg_node *node = kzalloc(sizeof *node, GFP_KERNEL);
> >>       if (!node)
> >>               return NULL;
> >>       node->vq = vq;
> >> --
> >> 2.8.1
> >
> > --
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