From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Tuesday, February 1, 2022 8:32 AM
>
> netvsc_device_remove() calls vunmap() inside which should not be
> called in the interrupt context. Current code calls hv_unmap_memory()
> in the free_netvsc_device() which is rcu callback and maybe called
> in the interrupt context. This will trigger BUG_ON(in_interrupt())
> in the vunmap(). Fix it via moving hv_unmap_memory() to netvsc_device_
> remove().
I think this change can fail to call hv_unmap_memory() in an error case.
If netvsc_init_buf() fails after hv_map_memory() succeeds for the receive
buffer or for the send buffer, no corresponding hv_unmap_memory() will
be done. The failure in netvsc_init_buf() will cause netvsc_connect_vsp()
to fail, so netvsc_add_device() will "goto close" where free_netvsc_device()
will be called. But free_netvsc_device() no longer calls hv_unmap_memory(),
so it won't ever happen. netvsc_device_remove() is never called in this case
because netvsc_add_device() failed.
Michael
>
> Fixes: 846da38de0e8 ("net: netvsc: Add Isolation VM support for netvsc driver")
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> drivers/net/hyperv/netvsc.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index afa81a9480cc..f989f920d4ce 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -154,19 +154,15 @@ static void free_netvsc_device(struct rcu_head *head)
>
> kfree(nvdev->extension);
>
> - if (nvdev->recv_original_buf) {
> - hv_unmap_memory(nvdev->recv_buf);
> + if (nvdev->recv_original_buf)
> vfree(nvdev->recv_original_buf);
> - } else {
> + else
> vfree(nvdev->recv_buf);
> - }
>
> - if (nvdev->send_original_buf) {
> - hv_unmap_memory(nvdev->send_buf);
> + if (nvdev->send_original_buf)
> vfree(nvdev->send_original_buf);
> - } else {
> + else
> vfree(nvdev->send_buf);
> - }
>
> bitmap_free(nvdev->send_section_map);
>
> @@ -765,6 +761,12 @@ void netvsc_device_remove(struct hv_device *device)
> netvsc_teardown_send_gpadl(device, net_device, ndev);
> }
>
> + if (net_device->recv_original_buf)
> + hv_unmap_memory(net_device->recv_buf);
> +
> + if (net_device->send_original_buf)
> + hv_unmap_memory(net_device->send_buf);
> +
> /* Release all resources */
> free_netvsc_device_rcu(net_device);
> }
> --
> 2.25.1
