[PATCH v3 2/6] s390/uvdevice: Add 'Add Secret' UVC

Steffen Eiden
2023-06-06T11:37:53Z

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@linux.ibm.com>
---
arch/s390/include/asm/uv.h | 14 +++++++
arch/s390/include/uapi/asm/uvdevice.h | 4 ++
drivers/s390/char/uvdevice.c | 57 +++++++++++++++++++++++++++
3 files changed, 75 insertions(+)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 28a9ad57b6f1..1babc70ea5d4 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 UV call struct for pv guests that contains a single address
+ * 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 inline int __uv_call(unsigned long r1, unsigned long r2)
{
int cc;
diff --git a/arch/s390/include/uapi/asm/uvdevice.h b/arch/s390/include/uapi/asm/uvdevice.h
index 9d9b684836c2..e77410226598 100644
--- a/arch/s390/include/uapi/asm/uvdevice.h
+++ b/arch/s390/include/uapi/asm/uvdevice.h
@@ -69,6 +69,7 @@ struct uvio_uvdev_info {
#define UVIO_ATT_ARCB_MAX_LEN 0x100000
#define UVIO_ATT_MEASUREMENT_MAX_LEN 0x8000
#define UVIO_ATT_ADDITIONAL_MAX_LEN 0x8000
+#define UVIO_ADD_SECRET_MAX_LEN 0x100000

#define UVIO_DEVICE_NAME "uv"
#define UVIO_TYPE_UVC 'u'
@@ -76,6 +77,7 @@ struct uvio_uvdev_info {
enum UVIO_IOCTL_NR {
UVIO_IOCTL_UVDEV_INFO_NR = 0x00,
UVIO_IOCTL_ATT_NR,
+ UVIO_IOCTL_ADD_SECRET_NR,
/* must be the last entry */
UVIO_IOCTL_NUM_IOCTLS
};
@@ -83,9 +85,11 @@ enum UVIO_IOCTL_NR {
#define UVIO_IOCTL(nr) _IOWR(UVIO_TYPE_UVC, nr, struct uvio_ioctl_cb)
#define UVIO_IOCTL_UVDEV_INFO UVIO_IOCTL(UVIO_IOCTL_UVDEV_INFO_NR)
#define UVIO_IOCTL_ATT UVIO_IOCTL(UVIO_IOCTL_ATT_NR)
+#define UVIO_IOCTL_ADD_SECRET UVIO_IOCTL(UVIO_IOCTL_ADD_SECRET_NR)

#define UVIO_SUPP_CALL(nr) (1ULL << (nr))
#define UVIO_SUPP_UDEV_INFO UVIO_SUPP_CALL(UVIO_IOCTL_UDEV_INFO_NR)
#define UVIO_SUPP_ATT UVIO_SUPP_CALL(UVIO_IOCTL_ATT_NR)
+#define UVIO_SUPP_ADD_SECRET UVIO_SUPP_CALL(UVIO_IOCTL_ADD_SECRET_NR)

#endif /* __S390_ASM_UVDEVICE_H */
diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index 4efeebcaf382..c10554bc1fee 100644
--- a/drivers/s390/char/uvdevice.c
+++ b/drivers/s390/char/uvdevice.c
@@ -37,6 +37,7 @@
static const u32 ioctl_nr_to_uvc_bit[] __initconst = {
[UVIO_IOCTL_UVDEV_INFO_NR] = BIT_UVIO_INTERNAL,
[UVIO_IOCTL_ATT_NR] = BIT_UVC_CMD_RETR_ATTEST,
+ [UVIO_IOCTL_ADD_SECRET_NR] = BIT_UVC_CMD_ADD_SECRET,
};

static_assert(ARRAY_SIZE(ioctl_nr_to_uvc_bit) == UVIO_IOCTL_NUM_IOCTLS);
@@ -231,6 +232,59 @@ static int uvio_attestation(struct uvio_ioctl_cb *uv_ioctl)
return ret;
}

+/** uvio_add_secret() - perform an Add Secret UVC
+ *
+ * @uv_ioctl: ioctl control block
+ *
+ * uvio_add_secret() performs the Add Secret Ultravisor Call. It verifies that
+ * the given userspace argument address is valid and its size is sane. Every
+ * other check is made by the Ultravisor (UV) and won't result in a negative
+ * return value. It copies the request to kernelspace, performs the UV-call, and
+ * copies the return codes to the ioctl control block. The argument has to point
+ * to an Add Secret Request Control Block. It is an encrypted and
+ * cryptographically verified request generated by userspace to insert the
+ * actual secret into the UV. 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.
+ *
+ * Context: might sleep
+ *
+ * Return: 0 on success or a negative error code on error.
+ */
+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 -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 +329,9 @@ 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;
--
2.40.1