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Message-ID: <5bd1d878-69d0-4d27-9129-6fb8126ccb31@linux.ibm.com>
Date: Mon, 4 Nov 2024 13:13:16 +0100
From: Janosch Frank <frankja@...ux.ibm.com>
To: Steffen Eiden <seiden@...ux.ibm.com>, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org
Cc: Ingo Franzki <ifranzki@...ux.ibm.com>,
Christoph Schlameuss <schlameuss@...ux.ibm.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>, borntraeger@...ux.ibm.com
Subject: Re: [PATCH v2] s390/uvdevice: Support longer secret lists
On 10/31/24 10:35 AM, Steffen Eiden wrote:
> Enable the list IOCTL to provide lists longer than on page (85 entries).
s/on/one/
> The list IOCTL accepts argument length up to 8 pages in page granularity
> and will fill 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.
Once the length check is fixed I'll be happy with this patch.
>
> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
> ---
> Reworked the whole list-creation loop. Hardened+simplified the implementation.
> Now, only the actual data filled by the CP is copied to userspace.
>
> arch/s390/include/uapi/asm/uvdevice.h | 1 +
> drivers/s390/char/uvdevice.c | 72 ++++++++++++++++++++-------
> 2 files changed, 54 insertions(+), 19 deletions(-)
>
> diff --git a/arch/s390/include/uapi/asm/uvdevice.h b/arch/s390/include/uapi/asm/uvdevice.h
> index 4947f26ad9fb..c584250d4a35 100644
> --- a/arch/s390/include/uapi/asm/uvdevice.h
> +++ b/arch/s390/include/uapi/asm/uvdevice.h
> @@ -71,6 +71,7 @@ struct uvio_uvdev_info {
> #define UVIO_ATT_ADDITIONAL_MAX_LEN 0x8000
> #define UVIO_ADD_SECRET_MAX_LEN 0x100000
> #define UVIO_LIST_SECRETS_LEN 0x1000
> +#define UVIO_LIST_SECRETS_MAX_LEN 0x8000
Since we're only ever allocating a page in the kernel it doesn't really
make sense to arbitrarily limit this IMHO.
A check for 0 and page alignment should be enough.
> #define UVIO_RETR_SECRET_MAX_LEN 0x2000
>
> #define UVIO_DEVICE_NAME "uv"
> diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
> index 1f90976293e8..667d573e54b0 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-UVC until there is no more
list secrets UVC
> + * 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 len must be a multiple of a page; 1-8 pages allowed.
Fix comment when adjusting len check.
> + * 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.
> + *
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