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.
Reported-by: [email protected]
Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
Signed-off-by: Jason Wang <[email protected]>
---
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
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?
Thanks,
Darren.
>
>Reported-by: [email protected]
>Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
>Signed-off-by: Jason Wang <[email protected]>
>---
> 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
>
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: [email protected]
>> Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting
>> backend")
>> Signed-off-by: Jason Wang <[email protected]>
>> ---
>> 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
>>
On Tue, Mar 27, 2018 at 05:43:14PM +0800, Jason Wang wrote:
>
>
> 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
Let's be a bit more specific about the problem maybe?
when vhost's attempt to start polling a descriptor fails, we remove the
poll->wqh entry from wait queue but do not clear it, so the following
cleanup (e.g. on release) will attempt to remove it again.
To fix, switch to vhost_poll_stop() which zeros poll->wqh
after removing poll from waitqueue to make sure it won't be freed twice."
the patch itself is fine though:
Acked-by: Michael S. Tsirkin <[email protected]>
> >
> > Thanks,
> >
> > Darren.
> >
> > >
> > > Reported-by: [email protected]
> > > Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting
> > > backend")
> > > Signed-off-by: Jason Wang <[email protected]>
> > > ---
> > > 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
> > >