linux-kernel - Re: [PATCH v2 2/6] s390/uvdevice: Add 'Add Secret' UVC

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Date:   Mon, 5 Jun 2023 15:19:50 +0200
From:   Janosch Frank <frankja@...ux.ibm.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        Viktor Mihajlovski <mihajlov@...ux.ibm.com>
Cc:     Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Nico Boehr <nrb@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Hendrik Brueckner <brueckner@...ux.ibm.com>
Subject: Re: [PATCH v2 2/6] s390/uvdevice: Add 'Add Secret' UVC

On 5/19/23 11:37, Steffen Eiden wrote:
> Userspace can call the Add Secret Ultravisor Call
> using IOCTLs on the uvdevice.
> During the handling of the new IOCTL nr the uvdevice will do some sanity
> checks first. Then, copy the request data to kernel space, perform the
> Ultravisor command, and copy the return codes to userspace.
> If the Add Secret UV facility is not present,
> UV will return invalid command rc. This won't be fenced in the driver
> and does not result in a negative return value. This is also true for
> any other possible error code the UV can return.
> 
> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
> ---
>   arch/s390/include/asm/uv.h            | 14 +++++++
>   arch/s390/include/uapi/asm/uvdevice.h |  4 ++
>   drivers/s390/char/uvdevice.c          | 58 +++++++++++++++++++++++++++
>   3 files changed, 76 insertions(+)
> 
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index 28a9ad57b6f1..a7dff64e1e24 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -58,6 +58,7 @@
>   #define UVC_CMD_SET_SHARED_ACCESS	0x1000
>   #define UVC_CMD_REMOVE_SHARED_ACCESS	0x1001
>   #define UVC_CMD_RETR_ATTEST		0x1020
> +#define UVC_CMD_ADD_SECRET		0x1031
>   
>   /* Bits in installed uv calls */
>   enum uv_cmds_inst {
> @@ -88,6 +89,7 @@ enum uv_cmds_inst {
>   	BIT_UVC_CMD_DUMP_CPU = 26,
>   	BIT_UVC_CMD_DUMP_COMPLETE = 27,
>   	BIT_UVC_CMD_RETR_ATTEST = 28,
> +	BIT_UVC_CMD_ADD_SECRET = 29,
>   };
>   
>   enum uv_feat_ind {
> @@ -292,6 +294,18 @@ struct uv_cb_dump_complete {
>   	u64 reserved30[5];
>   } __packed __aligned(8);
>   
> +/*
> + * A common call for pv guests that contains a single address

control block struct

> + * Examples:
> + * Add Secret
> + */
> +struct uv_cb_guest_addr {
> +	struct uv_cb_header header;
> +	u64 reserved08[3];
> +	u64 addr;
> +	u64 reserved28[4];
> +} __packed __aligned(8);
> +
[...]

> +static int uvio_add_secret(struct uvio_ioctl_cb *uv_ioctl)
> +{
> +	void __user *user_buf_arg = (void __user *)uv_ioctl->argument_addr;
> +	struct uv_cb_guest_addr uvcb = {
> +		.header.len = sizeof(uvcb),
> +		.header.cmd = UVC_CMD_ADD_SECRET,
> +	};
> +	void *asrcb = NULL;
> +	int ret;
> +
> +	if (uv_ioctl->argument_len > UVIO_ADD_SECRET_MAX_LEN)
> +		return -EINVAL;
> +	if (uv_ioctl->argument_len == 0)
> +		return -EINVAL;
> +
> +	asrcb = kvzalloc(uv_ioctl->argument_len, GFP_KERNEL);
> +	if (!asrcb)
> +		return -EINVAL;

-ENOMEM

> +
> +	ret = -EFAULT;
> +	if (copy_from_user(asrcb, user_buf_arg, uv_ioctl->argument_len))
> +		goto out;
> +
> +	ret = 0;
> +	uvcb.addr = (u64)asrcb;
> +	uv_call_sched(0, (u64)&uvcb);
> +	uv_ioctl->uv_rc = uvcb.header.rc;
> +	uv_ioctl->uv_rrc = uvcb.header.rrc;
> +
> +out:
> +	kvfree(asrcb);
> +	return ret;
> +}
> +
>   static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp,
>   				     unsigned long cmd)
>   {
> @@ -275,6 +330,9 @@ static long uvio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>   	case UVIO_IOCTL_ATT_NR:
>   		ret = uvio_attestation(&uv_ioctl);
>   		break;
> +	case UVIO_IOCTL_ADD_SECRET_NR:
> +		ret = uvio_add_secret(&uv_ioctl);
> +		break;
>   	default:
>   		ret = -ENOIOCTLCMD;
>   		break;