From: Melbin K Mathew <[email protected]>
The credit calculation in virtio_transport_get_credit() uses unsigned
arithmetic:
ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
If the peer shrinks its advertised buffer (peer_buf_alloc) while bytes
are in flight, the subtraction can underflow and produce a large
positive value, potentially allowing more data to be queued than the
peer can handle.
Reuse virtio_transport_has_space() which already handles this case and
add a comment to make it clear why we are doing that.
Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")
Suggested-by: Stefano Garzarella <[email protected]>
Signed-off-by: Melbin K Mathew <[email protected]>
[Stefano: use virtio_transport_has_space() instead of duplicating the code]
[Stefano: tweak the commit message]
Signed-off-by: Stefano Garzarella <[email protected]>
---
net/vmw_vsock/virtio_transport_common.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c
b/net/vmw_vsock/virtio_transport_common.c
index dcc8a1d5851e..2fe341be6ce2 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -28,6 +28,7 @@
static void virtio_transport_cancel_close_work(struct vsock_sock *vsk,
bool cancel_timeout);
+static s64 virtio_transport_has_space(struct virtio_vsock_sock *vvs);
static const struct virtio_transport *
virtio_transport_get_ops(struct vsock_sock *vsk)
@@ -499,9 +500,7 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock
*vvs, u32 credit)
return 0;
spin_lock_bh(&vvs->tx_lock);
- ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
- if (ret > credit)
- ret = credit;
+ ret = min_t(u32, credit, virtio_transport_has_space(vvs));
vvs->tx_cnt += ret;
vvs->bytes_unsent += ret;
spin_unlock_bh(&vvs->tx_lock);
@@ -877,11 +876,14 @@ u32 virtio_transport_seqpacket_has_data(struct vsock_sock
*vsk)
}
EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_has_data);
-static s64 virtio_transport_has_space(struct vsock_sock *vsk)
+static s64 virtio_transport_has_space(struct virtio_vsock_sock *vvs)
{
- struct virtio_vsock_sock *vvs = vsk->trans;
s64 bytes;
+ /* Use s64 arithmetic so if the peer shrinks peer_buf_alloc while
+ * we have bytes in flight (tx_cnt - peer_fwd_cnt), the subtraction
+ * does not underflow.
+ */
bytes = (s64)vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
if (bytes < 0)
bytes = 0;
@@ -895,7 +897,7 @@ s64 virtio_transport_stream_has_space(struct vsock_sock
*vsk)
s64 bytes;
spin_lock_bh(&vvs->tx_lock);
- bytes = virtio_transport_has_space(vsk);
+ bytes = virtio_transport_has_space(vvs);
spin_unlock_bh(&vvs->tx_lock);
return bytes;
@@ -1490,7 +1492,7 @@ static bool virtio_transport_space_update(struct sock *sk,
spin_lock_bh(&vvs->tx_lock);
vvs->peer_buf_alloc = le32_to_cpu(hdr->buf_alloc);
vvs->peer_fwd_cnt = le32_to_cpu(hdr->fwd_cnt);
- space_available = virtio_transport_has_space(vsk);
+ space_available = virtio_transport_has_space(vvs);
spin_unlock_bh(&vvs->tx_lock);
return space_available;
}
--
2.52.0
