diff options
| author | Melbin K Mathew <mlbnkm1@gmail.com> | 2026-01-21 10:36:25 +0100 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-01-22 15:41:33 +0100 |
| commit | 3ef3d52a1a9860d094395c7a3e593f3aa26ff012 (patch) | |
| tree | 9f7e77c2709e0a74fe926fc910588e53ec12b06d | |
| parent | ca1bb3fedf26a08ed31974131bc0064d4fe33649 (diff) | |
vsock/virtio: fix potential underflow in virtio_transport_get_credit()
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 <sgarzare@redhat.com>
Signed-off-by: Melbin K Mathew <mlbnkm1@gmail.com>
[Stefano: use virtio_transport_has_space() instead of duplicating the code]
[Stefano: tweak the commit message]
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Luigi Leonardi <leonardi@redhat.com>
Link: https://patch.msgid.link/20260121093628.9941-2-sgarzare@redhat.com
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | net/vmw_vsock/virtio_transport_common.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index 26b979ad71f0..6175124d63d3 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; @@ -1492,7 +1494,7 @@ 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; } |