From: Alexey Kardashevskiy <aik@amd.com>
To: Dan Williams <dan.j.williams@intel.com>, linux-coco@lists.linux.dev
Cc: Borislav Petkov <bp@alien8.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
Dionna Glaze <dionnaglaze@google.com>,
Brijesh Singh <brijesh.singh@amd.com>,
Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
peterz@infradead.org, dave.hansen@linux.intel.com
Subject: Re: [PATCH v6 6/7] virt: sevguest: Add TSM_REPORTS support for SNP_GET_EXT_REPORT
Date: Mon, 16 Oct 2023 22:36:28 +1100 [thread overview]
Message-ID: <3e8aae49-010c-43be-888b-b3ed9ad85610@amd.com> (raw)
In-Reply-To: <169716326994.984874.4170603294020542086.stgit@dwillia2-xfh.jf.intel.com>
On 13/10/23 13:14, Dan Williams wrote:
> The sevguest driver was a first mover in the confidential computing
> space. As a first mover that afforded some leeway to build the driver
> without concern for common infrastructure.
>
> Now that sevguest is no longer a singleton [1] the common operation of
> building and transmitting attestation report blobs can / should be made
> common. In this model the so called "TSM-provider" implementations can
> share a common envelope ABI even if the contents of that envelope remain
> vendor-specific. When / if the industry agrees on an attestation record
> format, that definition can also fit in the same ABI. In the meantime
> the kernel's maintenance burden is reduced and collaboration on the
> commons is increased.
>
> Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the data that
> the SNP_GET_EXT_REPORT ioctl produces. An example flow follows for
> retrieving the report blob via the TSM interface utility,
> assuming no nonce and VMPL==2:
>
> report=/sys/kernel/config/tsm/report/report0
> mkdir $report
> echo 2 > $report/privlevel
> dd if=/dev/urandom bs=64 count=1 > $report/inblob
Is not this one a "nonce"?
> hexdump -C $report/outblob # SNP report
> hexdump -C $report/auxblob # cert_table
> rmdir $report
>
> Given that the platform implementation is free to return empty
> certificate data if none is available it lets configfs-tsm be simplified
> as it only needs to worry about wrapping SNP_GET_EXT_REPORT, and leave
> SNP_GET_REPORT alone.
>
> The old ioctls can be lazily deprecated, the main motivation of this
> effort is to stop the proliferation of new ioctls, and to increase
> cross-vendor collaboration.
>
> Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1]
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Dionna Glaze <dionnaglaze@google.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
> Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/virt/coco/sev-guest/Kconfig | 1
> drivers/virt/coco/sev-guest/sev-guest.c | 133 +++++++++++++++++++++++++++++++
> 2 files changed, 134 insertions(+)
>
> diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig
> index da2d7ca531f0..1cffc72c41cb 100644
> --- a/drivers/virt/coco/sev-guest/Kconfig
> +++ b/drivers/virt/coco/sev-guest/Kconfig
> @@ -5,6 +5,7 @@ config SEV_GUEST
> select CRYPTO
> select CRYPTO_AEAD2
> select CRYPTO_GCM
> + select TSM_REPORTS
> help
> SEV-SNP firmware provides the guest a mechanism to communicate with
> the PSP without risk from a malicious hypervisor who wishes to read,
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index e5f8f115f4af..f3ca083127af 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -16,10 +16,12 @@
> #include <linux/miscdevice.h>
> #include <linux/set_memory.h>
> #include <linux/fs.h>
> +#include <linux/tsm.h>
> #include <crypto/aead.h>
> #include <linux/scatterlist.h>
> #include <linux/psp-sev.h>
> #include <linux/sockptr.h>
> +#include <linux/cleanup.h>
> #include <uapi/linux/sev-guest.h>
> #include <uapi/linux/psp-sev.h>
>
> @@ -768,6 +770,129 @@ static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno
> return key;
> }
>
> +struct snp_msg_report_resp_hdr {
> + u32 status;
> + u32 report_size;
> + u8 rsvd[24];
> +};
> +#define SNP_REPORT_INVALID_PARAM 0x16
There is one already - SEV_RET_INVALID_PARAM, defined in "Secure
Encrypted Virtualization API".
> +#define SNP_REPORT_INVALID_KEY_SEL 0x27
This one needs to be defined in include/uapi/linux/psp-sev.h's sev_ret_code.
> +
> +struct snp_msg_cert_entry {
> + unsigned char guid[16];
> + u32 offset;
> + u32 length;
> +};
> +
> +static int sev_report_new(struct tsm_report *report, void *data)
> +{
> + static const struct snp_msg_cert_entry zero_ent = { 0 };
> + struct snp_msg_cert_entry *cert_table;
> + struct tsm_desc *desc = &report->desc;
> + struct snp_guest_dev *snp_dev = data;
> + struct snp_msg_report_resp_hdr hdr;
> + const int report_size = SZ_4K;
> + const int ext_size = SEV_FW_BLOB_MAX_SIZE;
These two are size_t. Or u32. "int" is just weird :)
> + int ret, size = report_size + ext_size;
> + u32 certs_size, i;
@certs_size is size_t (as it is copied to ->auxblob_len in the end), and
@size is size_t as well.
@i is just "unsigned", can be declared right in the "for" below?
> +
> + if (desc->inblob_len != 64)
64 is either ext_req.data.user_data or TSM_INBLOB_MAX really.
May be even BUILD_BUG_ON(TSM_INBLOB_MAX != sizeof(ext_req.data.user_data)) ?
> + return -EINVAL;
> +
> + void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
I did not realize declaring variables in a middle of a scope is allowed
now :)
Since you are doing this, move zero_ent below. Or, better, use
guid_is_null().
> + if (!buf)
> + return -ENOMEM;
> +
> + guard(mutex)(&snp_cmd_mutex);
> +
> + /* Check if the VMPCK is not empty */
> + if (is_vmpck_empty(snp_dev)) {
> + dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
> + return -ENOTTY;
> + }
> +
> + cert_table = buf + report_size;
> + struct snp_ext_report_req ext_req = {
> + .data = { .vmpl = desc->privlevel },
> + .certs_address = (__u64)cert_table,
> + .certs_len = ext_size,
> + };
> + memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len);
> +
> + struct snp_guest_request_ioctl input = {
> + .msg_version = 1,
> + .req_data = (__u64)&ext_req,
> + .resp_data = (__u64)buf,
> + .exitinfo2 = 0xff,
Not sure we need this line with 0xff.
The GHCB spec says the hypervisor sets it, not the guest. And I could
not figure out why exactly snp_guest_ioctl() does "input.exitinfo2 =
0xff", my best guest it is to catch GHCB not being called before copying
memory to user.
> + };
> + struct snp_req_resp io = {
> + .req_data = KERNEL_SOCKPTR(&ext_req),
> + .resp_data = KERNEL_SOCKPTR(buf),
> + };
> +
> + ret = get_ext_report(snp_dev, &input, &io);
> +
Unnecessary empty line.
> + if (ret)
> + return ret;
> +
> + memcpy(&hdr, buf, sizeof(hdr));
> + if (hdr.status == SNP_REPORT_INVALID_PARAM)
> + return -EINVAL;
> + if (hdr.status == SNP_REPORT_INVALID_KEY_SEL)
> + return -EINVAL;
> + if (hdr.status)
> + return -ENXIO;
> + if ((hdr.report_size + sizeof(hdr)) > report_size)
> + return -ENOMEM;
> +
> + void *rbuf __free(kvfree) = kvzalloc(hdr.report_size, GFP_KERNEL);
> + if (!rbuf)
> + return -ENOMEM;
> +
> + memcpy(rbuf, buf + sizeof(hdr), hdr.report_size);
> + report->outblob = no_free_ptr(rbuf);
> + report->outblob_len = hdr.report_size;
> +
> + certs_size = 0;
> + for (i = 0; i < ext_size / sizeof(struct snp_msg_cert_entry); i++) {
> + if (memcmp(&cert_table[i], &zero_ent, sizeof(zero_ent)) == 0)
> + break;
> + certs_size = max(certs_size, cert_table[i].offset + cert_table[i].length);
> + }
> +
> + /* No certs to report */
> + if (!certs_size)
Nit: WARN_ON_ONCE(i) here?
> + return 0;
> +
> + /*
> + * cert_table reports more data than fits in ext_size the
> + * userspace cert_table walker can decide what happens next,
> + * truncate the output
> + */
> + if (certs_size > ext_size)
> + certs_size = ext_size;
This sounds more like the HV provided a broken table with offset(s)
ouside of the certs buffer. The HV is expected instead return
SW_EXITINFO2=0x0000000100000000 and RBX=requred_pages_number, and the
guest to retry.
> +
> + void *cbuf __free(kvfree) = kvzalloc(certs_size, GFP_KERNEL);
> + if (!cbuf)
> + return -ENOMEM;
In a such (unlikely) event the function returns an error but does not
free report->outblob which is going to leak if consequent call succeded.
This new no_free_ptr business is confusing at times :(
> +
> + memcpy(cbuf, cert_table, certs_size);
> + report->auxblob = no_free_ptr(cbuf);
> + report->auxblob_len = certs_size;
Aaaand, it works, so:
Tested-by: Alexey Kardashevskiy <aik@amd.com>
Thanks,
> +
> + return 0;
> +}
> +
> +static const struct tsm_ops sev_tsm_ops = {
> + .name = KBUILD_MODNAME,
> + .report_new = sev_report_new,
> +};
> +
> +static void unregister_sev_tsm(void *data)
> +{
> + tsm_unregister(&sev_tsm_ops);
> +}
> +
> static int __init sev_guest_probe(struct platform_device *pdev)
> {
> struct snp_secrets_page_layout *layout;
> @@ -841,6 +966,14 @@ static int __init sev_guest_probe(struct platform_device *pdev)
> snp_dev->input.resp_gpa = __pa(snp_dev->response);
> snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>
> + ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_ext_type);
> + if (ret)
> + goto e_free_cert_data;
> +
> + ret = devm_add_action_or_reset(&pdev->dev, unregister_sev_tsm, NULL);
> + if (ret)
> + goto e_free_cert_data;
> +
> ret = misc_register(misc);
> if (ret)
> goto e_free_cert_data;
>
--
Alexey
next prev parent reply other threads:[~2023-10-16 11:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-13 2:13 [PATCH v6 0/7] configfs-tsm: Attestation Report ABI Dan Williams
2023-10-13 2:14 ` [PATCH v6 1/7] virt: sevguest: Fix passing a stack buffer as a scatterlist target Dan Williams
2023-10-13 2:14 ` [PATCH v6 2/7] virt: coco: Add a coco/Makefile and coco/Kconfig Dan Williams
2023-10-13 2:14 ` [PATCH v6 3/7] configfs-tsm: Introduce a shared ABI for attestation reports Dan Williams
2023-10-13 4:43 ` Dionna Amalie Glaze
2023-10-13 5:15 ` Dan Williams
2023-10-16 6:36 ` Alexey Kardashevskiy
2023-10-17 2:19 ` Dan Williams
2023-10-17 6:20 ` Alexey Kardashevskiy
2023-10-19 1:29 ` Dan Williams
2023-10-19 20:24 ` Dan Williams
2023-10-13 2:14 ` [PATCH v6 4/7] virt: sevguest: Prep for kernel internal get_ext_report() Dan Williams
2023-10-13 2:14 ` [PATCH v6 5/7] mm/slab: Add __free() support for kvfree Dan Williams
2023-10-13 2:14 ` [PATCH v6 6/7] virt: sevguest: Add TSM_REPORTS support for SNP_GET_EXT_REPORT Dan Williams
2023-10-13 15:38 ` Tom Lendacky
2023-10-14 4:46 ` Dan Williams
2023-10-16 11:36 ` Alexey Kardashevskiy [this message]
2023-10-16 15:39 ` Dionna Amalie Glaze
2023-10-16 15:42 ` Peter Gonda
2023-10-17 0:42 ` Alexey Kardashevskiy
2023-10-19 4:30 ` Dan Williams
2023-10-17 4:07 ` Dan Williams
2023-10-17 5:35 ` Alexey Kardashevskiy
2023-10-17 6:28 ` Alexey Kardashevskiy
2023-10-19 4:43 ` Dan Williams
2023-10-19 5:12 ` Alexey Kardashevskiy
2023-10-19 3:34 ` Dan Williams
2023-10-13 2:14 ` [PATCH v6 7/7] virt: tdx-guest: Add Quote generation support using TSM_REPORTS Dan Williams
2023-10-19 18:12 ` Peter Gonda
2023-10-13 15:39 ` [PATCH v6 0/7] configfs-tsm: Attestation Report ABI Tom Lendacky
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3e8aae49-010c-43be-888b-b3ed9ad85610@amd.com \
--to=aik@amd.com \
--cc=bp@alien8.de \
--cc=brijesh.singh@amd.com \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=dionnaglaze@google.com \
--cc=jpiotrowski@linux.microsoft.com \
--cc=linux-coco@lists.linux.dev \
--cc=peterz@infradead.org \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=thomas.lendacky@amd.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.