From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net] vhost: correctly remove wait queue during poll failure Date: Tue, 27 Mar 2018 17:43:14 +0800 Message-ID: References: <1522122442-30317-1-git-send-email-jasowang@redhat.com> <20180327092811.ikvssyxgb74nucb4@dhcp-10-175-199-170.vpn.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit To: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20180327092811.ikvssyxgb74nucb4@dhcp-10-175-199-170.vpn.oracle.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2018年03月27日 17:28, Darren Kenny wrote: > Hi Jason, > > On Tue, Mar 27, 2018 at 11:47:22AM +0800, Jason Wang wrote: >> We tried to remove vq poll from wait queue, but do not check whether >> or not it was in a list before. This will lead double free. Fixing >> this by checking poll->wqh to make sure it was in a list. > > This text seems at odds with the code below, instead of checking > poll-whq, you are removing that check... > > Maybe the text needs rewording? Yes, I admit it's bad, thanks for pointing out. How about: "Fixing this by switching to use vhost_poll_stop() which zeros poll->wqh after removing poll from waitqueue to make sure it won't be freed twice." Thanks > > Thanks, > > Darren. > >> >> Reported-by: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com >> Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting >> backend") >> Signed-off-by: Jason Wang >> --- >> drivers/vhost/vhost.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >> index 1b3e8d2d..5d5a9d9 100644 >> --- a/drivers/vhost/vhost.c >> +++ b/drivers/vhost/vhost.c >> @@ -212,8 +212,7 @@ int vhost_poll_start(struct vhost_poll *poll, >> struct file *file) >>     if (mask) >>         vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask)); >>     if (mask & EPOLLERR) { >> -        if (poll->wqh) >> -            remove_wait_queue(poll->wqh, &poll->wait); >> +        vhost_poll_stop(poll); >>         ret = -EINVAL; >>     } >> >> -- >> 2.7.4 >>