diff mbox series

[v4,5/6] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT

Message ID 169570184829.596431.15991881056638719011.stgit@dwillia2-xfh.jf.intel.com
State New
Headers
Series configfs-tsm: Attestation Report ABI |

Commit Message

Dan Williams Sept. 26, 2023, 4:17 a.m. UTC 
  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
    hexdump -C $report/outblob
    cat $report/certs
    rmdir $report

Given that the platform implementation is free to return empty certificate data
if none is available it lets configfs-tsm be simplified if it only needs
to worry about one output format.

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.

Note, only compile-tested.

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>
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 |  130 +++++++++++++++++++++++++++++++
 2 files changed, 131 insertions(+)

Comments

Dan Carpenter Oct. 4, 2023, 8:22 a.m. UTC | #1 
Hi Dan,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Williams/virt-coco-Add-a-coco-Makefile-and-coco-Kconfig/20230926-121843
base:   6465e260f48790807eef06b583b38ca9789b6072
patch link:    https://lore.kernel.org/r/169570184829.596431.15991881056638719011.stgit%40dwillia2-xfh.jf.intel.com
patch subject: [PATCH v4 5/6] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT
config: x86_64-randconfig-161-20231002 (https://download.01.org/0day-ci/archive/20231003/202310030341.zaOu0ew0-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231003/202310030341.zaOu0ew0-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202310030341.zaOu0ew0-lkp@intel.com/

smatch warnings:
drivers/virt/coco/sev-guest/sev-guest.c:853 sev_report_new() error: uninitialized symbol 'certs_size'.

vim +/certs_size +853 drivers/virt/coco/sev-guest/sev-guest.c

80013405d5b7c6 Dan Williams 2023-09-25  778  static int sev_report_new(struct tsm_report *report, void *data)
80013405d5b7c6 Dan Williams 2023-09-25  779  {
80013405d5b7c6 Dan Williams 2023-09-25  780  	static const struct snp_msg_cert_entry zero_ent = { 0 };
80013405d5b7c6 Dan Williams 2023-09-25  781  	struct tsm_desc *desc = &report->desc;
80013405d5b7c6 Dan Williams 2023-09-25  782  	struct snp_guest_dev *snp_dev = data;
80013405d5b7c6 Dan Williams 2023-09-25  783  	struct snp_msg_report_resp_hdr hdr;
80013405d5b7c6 Dan Williams 2023-09-25  784  	const int report_size = SZ_4K;
80013405d5b7c6 Dan Williams 2023-09-25  785  	const int ext_size = SZ_16K;
80013405d5b7c6 Dan Williams 2023-09-25  786  	int ret, size = report_size + ext_size;
80013405d5b7c6 Dan Williams 2023-09-25  787  	int certs_size, cert_count, i, offset;
80013405d5b7c6 Dan Williams 2023-09-25  788  	u8 *certs_address;
80013405d5b7c6 Dan Williams 2023-09-25  789  
80013405d5b7c6 Dan Williams 2023-09-25  790  	if (desc->inblob_len != 64)
80013405d5b7c6 Dan Williams 2023-09-25  791  		return -EINVAL;
80013405d5b7c6 Dan Williams 2023-09-25  792  
80013405d5b7c6 Dan Williams 2023-09-25  793  	void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
80013405d5b7c6 Dan Williams 2023-09-25  794  	if (!buf)
80013405d5b7c6 Dan Williams 2023-09-25  795  		return -ENOMEM;
80013405d5b7c6 Dan Williams 2023-09-25  796  
80013405d5b7c6 Dan Williams 2023-09-25  797  	guard(mutex)(&snp_cmd_mutex);

Hoho.  Need guard stuff and no warnings generated.  Perhaps I have added
all the new unlock functions.  :)

80013405d5b7c6 Dan Williams 2023-09-25  798  	certs_address = buf + report_size;
80013405d5b7c6 Dan Williams 2023-09-25  799  	struct snp_ext_report_req ext_req = {
80013405d5b7c6 Dan Williams 2023-09-25  800  		.data = { .vmpl = desc->privlevel },
80013405d5b7c6 Dan Williams 2023-09-25  801  		.certs_address = (__u64)certs_address,
80013405d5b7c6 Dan Williams 2023-09-25  802  		.certs_len = ext_size,
80013405d5b7c6 Dan Williams 2023-09-25  803  	};
80013405d5b7c6 Dan Williams 2023-09-25  804  	memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len);
80013405d5b7c6 Dan Williams 2023-09-25  805  
80013405d5b7c6 Dan Williams 2023-09-25  806  	struct snp_guest_request_ioctl input = {
80013405d5b7c6 Dan Williams 2023-09-25  807  		.msg_version = 1,
80013405d5b7c6 Dan Williams 2023-09-25  808  		.req_data = (__u64)&ext_req,
80013405d5b7c6 Dan Williams 2023-09-25  809  		.resp_data = (__u64)buf,
80013405d5b7c6 Dan Williams 2023-09-25  810  	};
80013405d5b7c6 Dan Williams 2023-09-25  811  	struct snp_req_resp io = {
80013405d5b7c6 Dan Williams 2023-09-25  812  		.req_data = KERNEL_SOCKPTR(&ext_req),
80013405d5b7c6 Dan Williams 2023-09-25  813  		.resp_data = KERNEL_SOCKPTR(buf),
80013405d5b7c6 Dan Williams 2023-09-25  814  	};
80013405d5b7c6 Dan Williams 2023-09-25  815  
80013405d5b7c6 Dan Williams 2023-09-25  816  	ret = get_ext_report(snp_dev, &input, &io);
80013405d5b7c6 Dan Williams 2023-09-25  817  
80013405d5b7c6 Dan Williams 2023-09-25  818  	if (ret)
80013405d5b7c6 Dan Williams 2023-09-25  819  		return ret;
80013405d5b7c6 Dan Williams 2023-09-25  820  
80013405d5b7c6 Dan Williams 2023-09-25  821  	memcpy(&hdr, buf, sizeof(hdr));
80013405d5b7c6 Dan Williams 2023-09-25  822  	if (hdr.status == SNP_REPORT_INVALID_PARAM)
80013405d5b7c6 Dan Williams 2023-09-25  823  		return -EINVAL;
80013405d5b7c6 Dan Williams 2023-09-25  824  	if (hdr.status == SNP_REPORT_INVALID_KEY_SEL)
80013405d5b7c6 Dan Williams 2023-09-25  825  		return -EINVAL;
80013405d5b7c6 Dan Williams 2023-09-25  826  	if (hdr.status)
80013405d5b7c6 Dan Williams 2023-09-25  827  		return -ENXIO;
80013405d5b7c6 Dan Williams 2023-09-25  828  	if ((hdr.report_size + sizeof(hdr)) > report_size)
80013405d5b7c6 Dan Williams 2023-09-25  829  		return -ENOMEM;
80013405d5b7c6 Dan Williams 2023-09-25  830  
80013405d5b7c6 Dan Williams 2023-09-25  831  	void *rbuf __free(kvfree) = kvzalloc(hdr.report_size, GFP_KERNEL);
80013405d5b7c6 Dan Williams 2023-09-25  832  	if (!rbuf)
80013405d5b7c6 Dan Williams 2023-09-25  833  		return -ENOMEM;
80013405d5b7c6 Dan Williams 2023-09-25  834  
80013405d5b7c6 Dan Williams 2023-09-25  835  	memcpy(rbuf, buf + sizeof(hdr), hdr.report_size);
80013405d5b7c6 Dan Williams 2023-09-25  836  	report->outblob = no_free_ptr(rbuf);
80013405d5b7c6 Dan Williams 2023-09-25  837  	report->outblob_len = hdr.report_size;
80013405d5b7c6 Dan Williams 2023-09-25  838  
80013405d5b7c6 Dan Williams 2023-09-25  839  	for (i = 0; i < ext_size / sizeof(struct snp_msg_cert_entry); i++) {
80013405d5b7c6 Dan Williams 2023-09-25  840  		struct snp_msg_cert_entry *certs = buf + report_size;
80013405d5b7c6 Dan Williams 2023-09-25  841  
80013405d5b7c6 Dan Williams 2023-09-25  842  		if (memcmp(&certs[i], &zero_ent, sizeof(zero_ent)) == 0)
80013405d5b7c6 Dan Williams 2023-09-25  843  			break;
80013405d5b7c6 Dan Williams 2023-09-25  844  		certs_size += certs[i].length;

certs_size needs to be initialized to zero.

80013405d5b7c6 Dan Williams 2023-09-25  845  	}
80013405d5b7c6 Dan Williams 2023-09-25  846  	cert_count = i;
80013405d5b7c6 Dan Williams 2023-09-25  847  
80013405d5b7c6 Dan Williams 2023-09-25  848  	/* No certs to report */
80013405d5b7c6 Dan Williams 2023-09-25  849  	if (cert_count == 0)
80013405d5b7c6 Dan Williams 2023-09-25  850  		return 0;
80013405d5b7c6 Dan Williams 2023-09-25  851  
80013405d5b7c6 Dan Williams 2023-09-25  852  	/* sanity check that the entire certs table with metadata fits */
80013405d5b7c6 Dan Williams 2023-09-25 @853  	if ((cert_count + 1) * sizeof(zero_ent) + certs_size > ext_size)
80013405d5b7c6 Dan Williams 2023-09-25  854  		return -ENXIO;
80013405d5b7c6 Dan Williams 2023-09-25  855  
80013405d5b7c6 Dan Williams 2023-09-25  856  	void *cbuf __free(kvfree) = kvzalloc(certs_size, GFP_KERNEL);
80013405d5b7c6 Dan Williams 2023-09-25  857  	if (!cbuf)
80013405d5b7c6 Dan Williams 2023-09-25  858  		return -ENOMEM;
80013405d5b7c6 Dan Williams 2023-09-25  859  
80013405d5b7c6 Dan Williams 2023-09-25  860  	/* Concatenate returned certs */
80013405d5b7c6 Dan Williams 2023-09-25  861  	for (i = 0, offset = 0; i < cert_count; i++) {
80013405d5b7c6 Dan Williams 2023-09-25  862  		struct snp_msg_cert_entry *certs = buf + report_size;
80013405d5b7c6 Dan Williams 2023-09-25  863  
80013405d5b7c6 Dan Williams 2023-09-25  864  		memcpy(cbuf + offset, certs_address + certs[i].offset, certs[i].length);
80013405d5b7c6 Dan Williams 2023-09-25  865  		offset += certs[i].length;
80013405d5b7c6 Dan Williams 2023-09-25  866  	}
80013405d5b7c6 Dan Williams 2023-09-25  867  
80013405d5b7c6 Dan Williams 2023-09-25  868  	report->certs = no_free_ptr(cbuf);
80013405d5b7c6 Dan Williams 2023-09-25  869  	report->certs_len = certs_size;
80013405d5b7c6 Dan Williams 2023-09-25  870  
80013405d5b7c6 Dan Williams 2023-09-25  871  	return 0;
80013405d5b7c6 Dan Williams 2023-09-25  872  }
diff mbox series

Patch

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 c3c9e9ea691f..646feb433b1c 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>
 
@@ -759,6 +761,126 @@  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
+#define SNP_REPORT_INVALID_KEY_SEL 0x27
+
+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 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 = SZ_16K;
+	int ret, size = report_size + ext_size;
+	int certs_size, cert_count, i, offset;
+	u8 *certs_address;
+
+	if (desc->inblob_len != 64)
+		return -EINVAL;
+
+	void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	guard(mutex)(&snp_cmd_mutex);
+	certs_address = buf + report_size;
+	struct snp_ext_report_req ext_req = {
+		.data = { .vmpl = desc->privlevel },
+		.certs_address = (__u64)certs_address,
+		.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,
+	};
+	struct snp_req_resp io = {
+		.req_data = KERNEL_SOCKPTR(&ext_req),
+		.resp_data = KERNEL_SOCKPTR(buf),
+	};
+
+	ret = get_ext_report(snp_dev, &input, &io);
+
+	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;
+
+	for (i = 0; i < ext_size / sizeof(struct snp_msg_cert_entry); i++) {
+		struct snp_msg_cert_entry *certs = buf + report_size;
+
+		if (memcmp(&certs[i], &zero_ent, sizeof(zero_ent)) == 0)
+			break;
+		certs_size += certs[i].length;
+	}
+	cert_count = i;
+
+	/* No certs to report */
+	if (cert_count == 0)
+		return 0;
+
+	/* sanity check that the entire certs table with metadata fits */
+	if ((cert_count + 1) * sizeof(zero_ent) + certs_size > ext_size)
+		return -ENXIO;
+
+	void *cbuf __free(kvfree) = kvzalloc(certs_size, GFP_KERNEL);
+	if (!cbuf)
+		return -ENOMEM;
+
+	/* Concatenate returned certs */
+	for (i = 0, offset = 0; i < cert_count; i++) {
+		struct snp_msg_cert_entry *certs = buf + report_size;
+
+		memcpy(cbuf + offset, certs_address + certs[i].offset, certs[i].length);
+		offset += certs[i].length;
+	}
+
+	report->certs = no_free_ptr(cbuf);
+	report->certs_len = certs_size;
+
+	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;
@@ -832,6 +954,14 @@  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;