RE: [RFC RFT PATCH 3/4] hv_nstvsc: Don't free decrypted memory

[Michael Kelley]

From: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> Sent: Wednesday, February 21, 2024 6:10 PM
> 

"Subject:" prefix should be hv_netvsc:

> On TDX it is possible for the untrusted host to cause

Same comment about TDX vs. CoCo VM.

> 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.
> 
> hv_nstvsc could free decrypted/shared pages if set_memory_decrypted()

s/hv_nstvsc/hv_netvsc/

> fails. Check the decrypted field in the gpadl before freeing in order to
> not leak the memory.
> 
> Only compile tested.
> 
> Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu@xxxxxxxxxx>
> Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: linux-hyperv@xxxxxxxxxxxxxxx
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> ---
>  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 a6fcbda64ecc..2b6ec979a62f 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++) {
> --
> 2.34.1