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 <20180427185501-mutt-send-email-mst@kernel.org>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Fri, 27 Apr 2018 18:11:31 +0200
Message-ID: <CACT4Y+b4fEOw=GjTsZMHVyQPOZmuqPWj6AJJshpS-UGRx=bhXA@mail.gmail.com>
Subject: Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Kevin Easton <kevin@guarana.org>, Jason Wang <jasowang@redhat.com>,
        KVM list <kvm@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Fri, Apr 27, 2018 at 6:05 PM, Michael S. Tsirkin <mst@redhat.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@guarana.org>
>> Reported-by: syzbot+87cfa083e727a224754b@syzkaller.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.

>> ---
>>  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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