Re: [PATCH v2 3/5] hv_netvsc: Don't free decrypted memory

[Kuppuswamy Sathyanarayanan]

On 3/11/24 9:15 AM, mhkelley58@xxxxxxxxx wrote:
> From: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
>
> In CoCo VMs it is possible for the untrusted host to cause
> set_memory_encrypted() or set_memory_decrypted() to fail such that an
> error is returned and the resulting memory is shared. Callers need to
> take care to handle these errors to avoid returning decrypted (shared)
> memory to the page allocator, which could lead to functional or security
> issues.
>
> The netvsc driver could free decrypted/shared pages if
> set_memory_decrypted() fails. Check the decrypted field in the gpadl
> to decide whether to free the memory.
>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
> ---
LGTM

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
>  drivers/net/hyperv/netvsc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 82e9796c8f5e..70b7f91fb96b 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -154,8 +154,11 @@ static void free_netvsc_device(struct rcu_head *head)
>  	int i;
>  
>  	kfree(nvdev->extension);
> -	vfree(nvdev->recv_buf);
> -	vfree(nvdev->send_buf);
> +
> +	if (!nvdev->recv_buf_gpadl_handle.decrypted)
> +		vfree(nvdev->recv_buf);
> +	if (!nvdev->send_buf_gpadl_handle.decrypted)
> +		vfree(nvdev->send_buf);
>  	bitmap_free(nvdev->send_section_map);
>  
>  	for (i = 0; i < VRSS_CHANNEL_MAX; i++) {

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer