Re: [PATCH net V2] vhost-vsock: fix use after free

[Jason Wang]

On 2018å09æ28æ 01:04, Michael S. Tsirkin wrote:
> On Thu, Sep 27, 2018 at 08:22:04PM +0800, Jason Wang wrote:
> > The access of vsock is not protected by vhost_vsock_lock. This may
> > lead to use after free since vhost_vsock_dev_release() may free the
> > pointer at the same time.
> >
> > Fix this by holding the lock during the access.
> >
> > Reported-by:syzbot+e3e074963495f92a89ed@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability")
> > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
> > Cc: Stefan Hajnoczi<stefanha@xxxxxxxxxx>
> > Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
> Wow is that really the best we can do?

For net/stable, probably yes.

>   A global lock on a data path
> operation?

It's already there, and the patch only increase the critical section.

>   Granted use after free is nasty but Stefan said he sees
> a way to fix it using a per socket refcount. He's on vacation
> until Oct 4 though ...

Stefan has acked the pacth, so I think it's ok? We can do optimization 
for -next on top.

Thanks