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 at syzkaller.appspotmail.com
Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability")
Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
Cc: Stefan Hajnoczi <stefanha at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
- V2: fix typos
- The patch is needed for -stable.
---
drivers/vhost/vsock.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 34bc3ab40c6d..7d0b292867fd 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -210,21 +210,27 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
struct vhost_vsock *vsock;
int len = pkt->len;
+ spin_lock_bh(&vhost_vsock_lock);
+
/* Find the vhost_vsock according to guest context id */
- vsock = vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid));
+ vsock = __vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid));
if (!vsock) {
virtio_transport_free_pkt(pkt);
+ spin_unlock_bh(&vhost_vsock_lock);
return -ENODEV;
}
if (pkt->reply)
atomic_inc(&vsock->queued_replies);
- spin_lock_bh(&vsock->send_pkt_list_lock);
+ spin_lock(&vsock->send_pkt_list_lock);
list_add_tail(&pkt->list, &vsock->send_pkt_list);
- spin_unlock_bh(&vsock->send_pkt_list_lock);
+ spin_unlock(&vsock->send_pkt_list_lock);
vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
+
+ spin_unlock_bh(&vhost_vsock_lock);
+
return len;
}
@@ -236,18 +242,22 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
int cnt = 0;
LIST_HEAD(freeme);
+ spin_lock_bh(&vhost_vsock_lock);
+
/* Find the vhost_vsock according to guest context id */
- vsock = vhost_vsock_get(vsk->remote_addr.svm_cid);
- if (!vsock)
+ vsock = __vhost_vsock_get(vsk->remote_addr.svm_cid);
+ if (!vsock) {
+ spin_unlock_bh(&vhost_vsock_lock);
return -ENODEV;
+ }
- spin_lock_bh(&vsock->send_pkt_list_lock);
+ spin_lock(&vsock->send_pkt_list_lock);
list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
if (pkt->vsk != vsk)
continue;
list_move(&pkt->list, &freeme);
}
- spin_unlock_bh(&vsock->send_pkt_list_lock);
+ spin_unlock(&vsock->send_pkt_list_lock);
list_for_each_entry_safe(pkt, n, &freeme, list) {
if (pkt->reply)
@@ -265,6 +275,8 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
vhost_poll_queue(&tx_vq->poll);
}
+ spin_unlock_bh(&vhost_vsock_lock);
+
return 0;
}
--
2.17.1
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 at syzkaller.appspotmail.com > Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability") > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > Cc: Stefan Hajnoczi <stefanha at redhat.com> > Signed-off-by: Jason Wang <jasowang at redhat.com> > --- > - V2: fix typos > - The patch is needed for -stable. > --- > drivers/vhost/vsock.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-)Thank you, Jason! Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 455 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20180927/ee5e478f/attachment-0001.sig>
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 at syzkaller.appspotmail.com > Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability") > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > Cc: Stefan Hajnoczi <stefanha at redhat.com> > Signed-off-by: Jason Wang <jasowang at redhat.com>Wow is that really the best we can do? A global lock on a data path operation? 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 ...> --- > - V2: fix typos > - The patch is needed for -stable. > --- > drivers/vhost/vsock.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c > index 34bc3ab40c6d..7d0b292867fd 100644 > --- a/drivers/vhost/vsock.c > +++ b/drivers/vhost/vsock.c > @@ -210,21 +210,27 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt) > struct vhost_vsock *vsock; > int len = pkt->len; > > + spin_lock_bh(&vhost_vsock_lock); > + > /* Find the vhost_vsock according to guest context id */ > - vsock = vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid)); > + vsock = __vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid)); > if (!vsock) { > virtio_transport_free_pkt(pkt); > + spin_unlock_bh(&vhost_vsock_lock); > return -ENODEV; > } > > if (pkt->reply) > atomic_inc(&vsock->queued_replies); > > - spin_lock_bh(&vsock->send_pkt_list_lock); > + spin_lock(&vsock->send_pkt_list_lock); > list_add_tail(&pkt->list, &vsock->send_pkt_list); > - spin_unlock_bh(&vsock->send_pkt_list_lock); > + spin_unlock(&vsock->send_pkt_list_lock); > > vhost_work_queue(&vsock->dev, &vsock->send_pkt_work); > + > + spin_unlock_bh(&vhost_vsock_lock); > + > return len; > } > > @@ -236,18 +242,22 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk) > int cnt = 0; > LIST_HEAD(freeme); > > + spin_lock_bh(&vhost_vsock_lock); > + > /* Find the vhost_vsock according to guest context id */ > - vsock = vhost_vsock_get(vsk->remote_addr.svm_cid); > - if (!vsock) > + vsock = __vhost_vsock_get(vsk->remote_addr.svm_cid); > + if (!vsock) { > + spin_unlock_bh(&vhost_vsock_lock); > return -ENODEV; > + } > > - spin_lock_bh(&vsock->send_pkt_list_lock); > + spin_lock(&vsock->send_pkt_list_lock); > list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) { > if (pkt->vsk != vsk) > continue; > list_move(&pkt->list, &freeme); > } > - spin_unlock_bh(&vsock->send_pkt_list_lock); > + spin_unlock(&vsock->send_pkt_list_lock); > > list_for_each_entry_safe(pkt, n, &freeme, list) { > if (pkt->reply) > @@ -265,6 +275,8 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk) > vhost_poll_queue(&tx_vq->poll); > } > > + spin_unlock_bh(&vhost_vsock_lock); > + > return 0; > } > > -- > 2.17.1
On 2018?09?28? 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 at syzkaller.appspotmail.com >> Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability") >> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") >> Cc: Stefan Hajnoczi<stefanha at redhat.com> >> Signed-off-by: Jason Wang<jasowang at redhat.com> > 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