linux-kernel - [PATCH v3] s390/uvdevice: Support longer secret lists

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Message-ID: <20241104153609.1361388-1-seiden@linux.ibm.com>
Date: Mon,  4 Nov 2024 16:36:09 +0100
From: Steffen Eiden <seiden@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc: Ingo Franzki <ifranzki@...ux.ibm.com>,
        Christoph Schlameuss <schlameuss@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>, borntraeger@...ux.ibm.com
Subject: [PATCH v3] s390/uvdevice: Support longer secret lists

Enable the list IOCTL to provide lists longer than one page (85 entries).
The list IOCTL now accepts any argument length in page granularity.
It fills the argument up to this length with entries until the list
ends. User space unaware of this enhancement will still receive one page
of data and an uv_rc 0x0100.

Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
---
 v3: remove upper boundary (8 pages) for arg len

 drivers/s390/char/uvdevice.c | 71 ++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 19 deletions(-)

diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index 1f90976293e8..7551b03d5f99 100644
--- a/drivers/s390/char/uvdevice.c
+++ b/drivers/s390/char/uvdevice.c
@@ -297,6 +297,43 @@ static int uvio_add_secret(struct uvio_ioctl_cb *uv_ioctl)
 	return ret;
 }
 
+/*
+ * Do the actual secret list creation. Calls the list secrets UVC until there
+ * is no more space in the user buffer, or the list ends.
+ */
+static int uvio_get_list(void *zpage, struct uvio_ioctl_cb *uv_ioctl)
+{
+	const size_t data_off = offsetof(struct uv_secret_list, secrets);
+	u8 __user *user_buf = (u8 __user *)uv_ioctl->argument_addr;
+	struct uv_secret_list *list = zpage;
+	u16 num_secrets_stored = 0;
+	size_t user_off = data_off;
+	size_t copy_len;
+
+	do {
+		uv_list_secrets(list, list->next_secret_idx, &uv_ioctl->uv_rc,
+				&uv_ioctl->uv_rrc);
+		if (uv_ioctl->uv_rc != UVC_RC_EXECUTED &&
+		    uv_ioctl->uv_rc != UVC_RC_MORE_DATA)
+			break;
+
+		copy_len = sizeof(list->secrets[0]) * list->num_secr_stored;
+		WARN_ON(copy_len > sizeof(list->secrets));
+
+		if (copy_to_user(user_buf + user_off, list->secrets, copy_len))
+			return -EFAULT;
+
+		user_off += copy_len;
+		num_secrets_stored += list->num_secr_stored;
+	} while (uv_ioctl->uv_rc == UVC_RC_MORE_DATA &&
+		 user_off + sizeof(*list) <= uv_ioctl->argument_len);
+
+	list->num_secr_stored = num_secrets_stored;
+	if (copy_to_user(user_buf, list, data_off))
+		return -EFAULT;
+	return 0;
+}
+
 /** uvio_list_secrets() - perform a List Secret UVC
  * @uv_ioctl: ioctl control block
  *
@@ -308,6 +345,12 @@ static int uvio_add_secret(struct uvio_ioctl_cb *uv_ioctl)
  *
  * The argument specifies the location for the result of the UV-Call.
  *
+ * Argument length must be a multiple of a page.
+ * The list secrets IOCTL will call the list UVC multiple times and fill
+ * the provided user-buffer with list elements until either the list ends or
+ * the buffer is full. The list header is merged over all list header from the
+ * individual UVCs.
+ *
  * If the List Secrets 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.
@@ -318,31 +361,21 @@ static int uvio_add_secret(struct uvio_ioctl_cb *uv_ioctl)
  */
 static int uvio_list_secrets(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_LIST_SECRETS,
-	};
-	void *secrets = NULL;
-	int ret = 0;
+	void *zpage = NULL;
+	int rc;
 
-	if (uv_ioctl->argument_len != UVIO_LIST_SECRETS_LEN)
+	if (uv_ioctl->argument_len == 0 ||
+	    uv_ioctl->argument_len % UVIO_LIST_SECRETS_LEN != 0)
 		return -EINVAL;
 
-	secrets = kvzalloc(UVIO_LIST_SECRETS_LEN, GFP_KERNEL);
-	if (!secrets)
+	zpage = (void *)get_zeroed_page(GFP_KERNEL);
+	if (!zpage)
 		return -ENOMEM;
 
-	uvcb.addr = (u64)secrets;
-	uv_call_sched(0, (u64)&uvcb);
-	uv_ioctl->uv_rc = uvcb.header.rc;
-	uv_ioctl->uv_rrc = uvcb.header.rrc;
-
-	if (copy_to_user(user_buf_arg, secrets, UVIO_LIST_SECRETS_LEN))
-		ret = -EFAULT;
+	rc = uvio_get_list(zpage, uv_ioctl);
 
-	kvfree(secrets);
-	return ret;
+	free_page((unsigned long)zpage);
+	return rc;
 }
 
 /** uvio_lock_secrets() - perform a Lock Secret Store UVC
-- 
2.45.2