| Message ID | 1522122442-30317-1-git-send-email-jasowang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com >Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend") >Signed-off-by: Jason Wang <jasowang@redhat.com> >--- > 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: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com >> Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting >> backend") >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> 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 <mst@redhat.com> > > > > Thanks, > > > > Darren. > > > > > > > > Reported-by: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com > > > Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting > > > backend") > > > Signed-off-by: Jason Wang <jasowang@redhat.com> > > > --- > > > 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 > > >
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; }
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: syzbot+c0272972b01b872e604a@syzkaller.appspotmail.com Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend") Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/vhost.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)