194 lines
6.0 KiB
Diff
194 lines
6.0 KiB
Diff
From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Mon, 5 Nov 2018 10:35:47 +0000
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Subject: vhost/vsock: fix use-after-free in network stack callers
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Origin: https://git.kernel.org/linus/834e772c8db0c6a275d75315d90aba4ebbb1e249
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-14625
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If the network stack calls .send_pkt()/.cancel_pkt() during .release(),
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a struct vhost_vsock use-after-free is possible. This occurs because
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.release() does not wait for other CPUs to stop using struct
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vhost_vsock.
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Switch to an RCU-enabled hashtable (indexed by guest CID) so that
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.release() can wait for other CPUs by calling synchronize_rcu(). This
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also eliminates vhost_vsock_lock acquisition in the data path so it
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could have a positive effect on performance.
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This is CVE-2018-14625 "kernel: use-after-free Read in vhost_transport_send_pkt".
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Cc: stable@vger.kernel.org
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Reported-and-tested-by: syzbot+bd391451452fb0b93039@syzkaller.appspotmail.com
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Reported-by: syzbot+e3e074963495f92a89ed@syzkaller.appspotmail.com
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Reported-by: syzbot+d5a0a170c5069658b141@syzkaller.appspotmail.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Acked-by: Jason Wang <jasowang@redhat.com>
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---
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drivers/vhost/vsock.c | 57 +++++++++++++++++++++++++------------------
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1 file changed, 33 insertions(+), 24 deletions(-)
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diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
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index 731e2ea2aeca..98ed5be132c6 100644
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--- a/drivers/vhost/vsock.c
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+++ b/drivers/vhost/vsock.c
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@@ -15,6 +15,7 @@
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#include <net/sock.h>
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#include <linux/virtio_vsock.h>
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#include <linux/vhost.h>
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+#include <linux/hashtable.h>
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#include <net/af_vsock.h>
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#include "vhost.h"
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@@ -27,14 +28,14 @@ enum {
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/* Used to track all the vhost_vsock instances on the system. */
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static DEFINE_SPINLOCK(vhost_vsock_lock);
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-static LIST_HEAD(vhost_vsock_list);
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+static DEFINE_READ_MOSTLY_HASHTABLE(vhost_vsock_hash, 8);
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struct vhost_vsock {
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struct vhost_dev dev;
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struct vhost_virtqueue vqs[2];
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- /* Link to global vhost_vsock_list, protected by vhost_vsock_lock */
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- struct list_head list;
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+ /* Link to global vhost_vsock_hash, writes use vhost_vsock_lock */
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+ struct hlist_node hash;
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struct vhost_work send_pkt_work;
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spinlock_t send_pkt_list_lock;
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@@ -50,11 +51,14 @@ static u32 vhost_transport_get_local_cid(void)
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return VHOST_VSOCK_DEFAULT_HOST_CID;
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}
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-static struct vhost_vsock *__vhost_vsock_get(u32 guest_cid)
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+/* Callers that dereference the return value must hold vhost_vsock_lock or the
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+ * RCU read lock.
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+ */
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+static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
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{
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struct vhost_vsock *vsock;
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- list_for_each_entry(vsock, &vhost_vsock_list, list) {
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+ hash_for_each_possible_rcu(vhost_vsock_hash, vsock, hash, guest_cid) {
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u32 other_cid = vsock->guest_cid;
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/* Skip instances that have no CID yet */
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@@ -69,17 +73,6 @@ static struct vhost_vsock *__vhost_vsock_get(u32 guest_cid)
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return NULL;
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}
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-static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
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-{
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- struct vhost_vsock *vsock;
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-
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- spin_lock_bh(&vhost_vsock_lock);
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- vsock = __vhost_vsock_get(guest_cid);
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- spin_unlock_bh(&vhost_vsock_lock);
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-
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- return vsock;
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-}
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-
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static void
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vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
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struct vhost_virtqueue *vq)
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@@ -210,9 +203,12 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
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struct vhost_vsock *vsock;
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int len = pkt->len;
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+ rcu_read_lock();
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+
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/* Find the vhost_vsock according to guest context id */
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vsock = vhost_vsock_get(le64_to_cpu(pkt->hdr.dst_cid));
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if (!vsock) {
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+ rcu_read_unlock();
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virtio_transport_free_pkt(pkt);
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return -ENODEV;
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}
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@@ -225,6 +221,8 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
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spin_unlock_bh(&vsock->send_pkt_list_lock);
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vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
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+
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+ rcu_read_unlock();
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return len;
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}
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@@ -234,12 +232,15 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
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struct vhost_vsock *vsock;
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struct virtio_vsock_pkt *pkt, *n;
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int cnt = 0;
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+ int ret = -ENODEV;
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LIST_HEAD(freeme);
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+ rcu_read_lock();
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+
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/* Find the vhost_vsock according to guest context id */
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vsock = vhost_vsock_get(vsk->remote_addr.svm_cid);
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if (!vsock)
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- return -ENODEV;
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+ goto out;
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spin_lock_bh(&vsock->send_pkt_list_lock);
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list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
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@@ -265,7 +266,10 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
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vhost_poll_queue(&tx_vq->poll);
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}
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- return 0;
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+ ret = 0;
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+out:
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+ rcu_read_unlock();
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+ return ret;
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}
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static struct virtio_vsock_pkt *
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@@ -533,10 +537,6 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
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spin_lock_init(&vsock->send_pkt_list_lock);
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INIT_LIST_HEAD(&vsock->send_pkt_list);
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vhost_work_init(&vsock->send_pkt_work, vhost_transport_send_pkt_work);
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-
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- spin_lock_bh(&vhost_vsock_lock);
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- list_add_tail(&vsock->list, &vhost_vsock_list);
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- spin_unlock_bh(&vhost_vsock_lock);
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return 0;
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out:
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@@ -585,9 +585,13 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
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struct vhost_vsock *vsock = file->private_data;
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spin_lock_bh(&vhost_vsock_lock);
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- list_del(&vsock->list);
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+ if (vsock->guest_cid)
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+ hash_del_rcu(&vsock->hash);
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spin_unlock_bh(&vhost_vsock_lock);
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+ /* Wait for other CPUs to finish using vsock */
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+ synchronize_rcu();
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+
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/* Iterating over all connections for all CIDs to find orphans is
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* inefficient. Room for improvement here. */
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vsock_for_each_connected_socket(vhost_vsock_reset_orphans);
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@@ -628,12 +632,17 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
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/* Refuse if CID is already in use */
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spin_lock_bh(&vhost_vsock_lock);
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- other = __vhost_vsock_get(guest_cid);
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+ other = vhost_vsock_get(guest_cid);
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if (other && other != vsock) {
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spin_unlock_bh(&vhost_vsock_lock);
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return -EADDRINUSE;
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}
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+
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+ if (vsock->guest_cid)
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+ hash_del_rcu(&vsock->hash);
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+
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vsock->guest_cid = guest_cid;
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+ hash_add_rcu(vhost_vsock_hash, &vsock->hash, guest_cid);
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spin_unlock_bh(&vhost_vsock_lock);
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return 0;
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--
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2.20.0.rc2
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