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xdp: fix potential deadlock on socket mutex

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There are 2 call chains:

  a) xsk_bind --> xdp_umem_assign_dev
  b) unregister_netdevice_queue --> xsk_notifier

with the following locking order:

  a) xs->mutex --> rtnl_lock
  b) rtnl_lock --> xdp.lock --> xs->mutex

Different order of taking 'xs->mutex' and 'rtnl_lock' could produce a
deadlock here. Fix that by moving the 'rtnl_lock' before 'xs->lock' in
the bind call chain (a).

Reported-by: syzbot+bf64ec93de836d7f4c2c@syzkaller.appspotmail.com
Fixes: 455302d1c9 ("xdp: fix hang while unregistering device bound to xdp socket")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Ilya Maximets 2019-07-08 14:03:44 +03:00 committed by Daniel Borkmann
parent 675716400d
commit 5464c3a0e9
2 changed files with 8 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
net/xdp/xdp_umem.c
View File

@ -87,21 +87,20 @@ int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
struct netdev_bpf bpf;
int err = 0;
ASSERT_RTNL();
force_zc = flags & XDP_ZEROCOPY;
force_copy = flags & XDP_COPY;
if (force_zc && force_copy)
return -EINVAL;
rtnl_lock();
if (xdp_get_umem_from_qid(dev, queue_id)) {
err = -EBUSY;
goto out_rtnl_unlock;
}
if (xdp_get_umem_from_qid(dev, queue_id))
return -EBUSY;
err = xdp_reg_umem_at_qid(dev, umem, queue_id);
if (err)
goto out_rtnl_unlock;
return err;
umem->dev = dev;
umem->queue_id = queue_id;
@ -110,7 +109,7 @@ int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
if (force_copy)
/* For copy-mode, we are done. */
goto out_rtnl_unlock;
return 0;
if (!dev->netdev_ops->ndo_bpf ||
!dev->netdev_ops->ndo_xsk_async_xmit) {
@ -125,7 +124,6 @@ int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
err = dev->netdev_ops->ndo_bpf(dev, &bpf);
if (err)
goto err_unreg_umem;
rtnl_unlock();
umem->zc = true;
return 0;
@ -135,8 +133,6 @@ int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
err = 0; /* fallback to copy mode */
if (err)
xdp_clear_umem_at_qid(dev, queue_id);
out_rtnl_unlock:
rtnl_unlock();
return err;
}

2
net/xdp/xsk.c
View File

@ -430,6 +430,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
if (flags & ~(XDP_SHARED_UMEM | XDP_COPY | XDP_ZEROCOPY))
return -EINVAL;
rtnl_lock();
mutex_lock(&xs->mutex);
if (xs->state != XSK_READY) {
err = -EBUSY;
@ -515,6 +516,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
xs->state = XSK_BOUND;
out_release:
mutex_unlock(&xs->mutex);
rtnl_unlock();
return err;
}