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Fix double fget() in vhost_net_set_backend()
commit fb4554c223
upstream.
Descriptor table is a shared resource; two fget() on the same descriptor
may return different struct file references. get_tap_ptr_ring() is
called after we'd found (and pinned) the socket we'll be using and it
tries to find the private tun/tap data structures associated with it.
Redoing the lookup by the same file descriptor we'd used to get the
socket is racy - we need to same struct file.
Thanks to Jason for spotting a braino in the original variant of patch -
I'd missed the use of fd == -1 for disabling backend, and in that case
we can end up with sock == NULL and sock != oldsock.
Cc: stable@kernel.org
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
b42e5e3a84
commit
ec0d801d1a
1 changed files with 7 additions and 8 deletions
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@ -1450,13 +1450,9 @@ static struct socket *get_raw_socket(int fd)
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return ERR_PTR(r);
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}
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static struct ptr_ring *get_tap_ptr_ring(int fd)
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static struct ptr_ring *get_tap_ptr_ring(struct file *file)
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{
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struct ptr_ring *ring;
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struct file *file = fget(fd);
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if (!file)
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return NULL;
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ring = tun_get_tx_ring(file);
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if (!IS_ERR(ring))
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goto out;
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@ -1465,7 +1461,6 @@ static struct ptr_ring *get_tap_ptr_ring(int fd)
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goto out;
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ring = NULL;
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out:
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fput(file);
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return ring;
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}
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@ -1552,8 +1547,12 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
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r = vhost_net_enable_vq(n, vq);
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if (r)
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goto err_used;
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if (index == VHOST_NET_VQ_RX)
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nvq->rx_ring = get_tap_ptr_ring(fd);
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if (index == VHOST_NET_VQ_RX) {
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if (sock)
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nvq->rx_ring = get_tap_ptr_ring(sock->file);
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else
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nvq->rx_ring = NULL;
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}
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oldubufs = nvq->ubufs;
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nvq->ubufs = ubufs;
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