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x86/sev: Change snp_guest_issue_request()'s fw_err argument 

[ Upstream commit 0144e3b85d ]

The GHCB specification declares that the firmware error value for
a guest request will be stored in the lower 32 bits of EXIT_INFO_2.  The
upper 32 bits are for the VMM's own error code. The fw_err argument to
snp_guest_issue_request() is thus a misnomer, and callers will need
access to all 64 bits.

The type of unsigned long also causes problems, since sw_exit_info2 is
u64 (unsigned long long) vs the argument's unsigned long*. Change this
type for issuing the guest request. Pass the ioctl command struct's error
field directly instead of in a local variable, since an incomplete guest
request may not set the error code, and uninitialized stack memory would
be written back to user space.

The firmware might not even be called, so bookend the call with the no
firmware call error and clear the error.

Since the "fw_err" field is really exitinfo2 split into the upper bits'
vmm error code and lower bits' firmware error code, convert the 64 bit
value to a union.

  [ bp:
   - Massage commit message
   - adjust code
   - Fix a build issue as
   Reported-by: kernel test robot <lkp@intel.com>
   Link: https://lore.kernel.org/oe-kbuild-all/202303070609.vX6wp2Af-lkp@intel.com
   - print exitinfo2 in hex
   Tom:
    - Correct -EIO exit case. ]

Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230214164638.1189804-5-dionnaglaze@google.com
Link: https://lore.kernel.org/r/20230307192449.24732-12-bp@alien8.de
Stable-dep-of: db10cb9b57 ("virt: sevguest: Fix passing a stack buffer as a scatterlist target")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dionna Glaze 2023-03-07 20:24:49 +01:00 committed by Greg Kroah-Hartman
parent a5b03f56d3
commit d889b7bc12
6 changed files with 83 additions and 56 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
Documentation/virt/coco/sev-guest.rst
View File

@ -37,11 +37,11 @@ along with a description:
the return value. General error numbers (-ENOMEM, -EINVAL)
are not detailed, but errors with specific meanings are.
The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
The ioctl accepts struct snp_user_guest_request. The input and output structure is
specified through the req_data and resp_data field respectively. If the ioctl fails
to execute due to a firmware error, then fw_err code will be set. Otherwise, fw_err
will be set to 0x00000000ffffffff, i.e., the lower 32-bits are -1.
The guest ioctl should be issued on a file descriptor of the /dev/sev-guest
device. The ioctl accepts struct snp_user_guest_request. The input and
output structure is specified through the req_data and resp_data field
respectively. If the ioctl fails to execute due to a firmware error, then
the fw_error code will be set, otherwise fw_error will be set to -1.
The firmware checks that the message sequence counter is one greater than
the guests message sequence counter. If guest driver fails to increment message
@ -57,8 +57,14 @@ counter (e.g. counter overflow), then -EIO will be returned.
__u64 req_data;
__u64 resp_data;
/* firmware error code on failure (see psp-sev.h) */
__u64 fw_err;
/* bits[63:32]: VMM error code, bits[31:0] firmware error code (see psp-sev.h) */
union {
__u64 exitinfo2;
struct {
__u32 fw_error;
__u32 vmm_error;
};
};
};
2.1 SNP_GET_REPORT

4
arch/x86/include/asm/sev-common.h
View File

@ -128,10 +128,6 @@ struct snp_psc_desc {
struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];
} __packed;
/* Guest message request error codes */
#define SNP_GUEST_REQ_INVALID_LEN BIT_ULL(32)
#define SNP_GUEST_REQ_ERR_BUSY BIT_ULL(33)
#define GHCB_MSR_TERM_REQ 0x100
#define GHCB_MSR_TERM_REASON_SET_POS 12
#define GHCB_MSR_TERM_REASON_SET_MASK 0xf

10
arch/x86/include/asm/sev.h
View File

@ -9,6 +9,8 @@
#define __ASM_ENCRYPTED_STATE_H
#include <linux/types.h>
#include <linux/sev-guest.h>
#include <asm/insn.h>
#include <asm/sev-common.h>
#include <asm/bootparam.h>
@ -185,6 +187,9 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate)
return rc;
}
struct snp_guest_request_ioctl;
void setup_ghcb(void);
void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
unsigned long npages);
@ -196,7 +201,7 @@ void snp_set_memory_private(unsigned long vaddr, unsigned long npages);
void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
void __init __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
@ -216,8 +221,7 @@ static inline void snp_set_memory_private(unsigned long vaddr, unsigned long npa
static inline void snp_set_wakeup_secondary_cpu(void) { }
static inline bool snp_init(struct boot_params *bp) { return false; }
static inline void snp_abort(void) { }
static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input,
unsigned long *fw_err)
static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
{
return -ENOTTY;
}

15
arch/x86/kernel/sev.c
View File

@ -22,6 +22,8 @@
#include <linux/efi.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/psp-sev.h>
#include <uapi/linux/sev-guest.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@ -2205,7 +2207,7 @@ static int __init init_sev_config(char *str)
}
__setup("sev=", init_sev_config);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err)
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
{
struct ghcb_state state;
struct es_em_ctxt ctxt;
@ -2213,8 +2215,7 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
struct ghcb *ghcb;
int ret;
if (!fw_err)
return -EINVAL;
rio->exitinfo2 = SEV_RET_NO_FW_CALL;
/*
* __sev_get_ghcb() needs to run with IRQs disabled because it is using
@ -2239,16 +2240,16 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
if (ret)
goto e_put;
*fw_err = ghcb->save.sw_exit_info_2;
switch (*fw_err) {
rio->exitinfo2 = ghcb->save.sw_exit_info_2;
switch (rio->exitinfo2) {
case 0:
break;
case SNP_GUEST_REQ_ERR_BUSY:
case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_BUSY):
ret = -EAGAIN;
break;
case SNP_GUEST_REQ_INVALID_LEN:
case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN):
/* Number of expected pages are returned in RBX */
if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
input->data_npages = ghcb_get_rbx(ghcb);

72
drivers/virt/coco/sev-guest/sev-guest.c
View File

@ -334,11 +334,12 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
return __enc_payload(snp_dev, req, payload, sz);
}
static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
struct snp_guest_request_ioctl *rio)
{
unsigned long err = 0xff, override_err = 0;
unsigned long req_start = jiffies;
unsigned int override_npages = 0;
u64 override_err = 0;
int rc;
retry_request:
@ -348,7 +349,7 @@ retry_request:
* sequence number must be incremented or the VMPCK must be deleted to
* prevent reuse of the IV.
*/
rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
rc = snp_issue_guest_request(exit_code, &snp_dev->input, rio);
switch (rc) {
case -ENOSPC:
/*
@ -366,7 +367,7 @@ retry_request:
* request buffer size was too small and give the caller the
* required buffer size.
*/
override_err = SNP_GUEST_REQ_INVALID_LEN;
override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN);
/*
* If this call to the firmware succeeds, the sequence number can
@ -379,7 +380,7 @@ retry_request:
goto retry_request;
/*
* The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
* The host may return SNP_GUEST_VMM_ERR_BUSY if the request has been
* throttled. Retry in the driver to avoid returning and reusing the
* message sequence number on a different message.
*/
@ -400,27 +401,29 @@ retry_request:
*/
snp_inc_msg_seqno(snp_dev);
if (fw_err)
*fw_err = override_err ?: err;
if (override_err) {
rio->exitinfo2 = override_err;
/*
* If an extended guest request was issued and the supplied certificate
* buffer was not large enough, a standard guest request was issued to
* prevent IV reuse. If the standard request was successful, return -EIO
* back to the caller as would have originally been returned.
*/
if (!rc && override_err == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
rc = -EIO;
}
if (override_npages)
snp_dev->input.data_npages = override_npages;
/*
* If an extended guest request was issued and the supplied certificate
* buffer was not large enough, a standard guest request was issued to
* prevent IV reuse. If the standard request was successful, return -EIO
* back to the caller as would have originally been returned.
*/
if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
return -EIO;
return rc;
}
static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
u8 type, void *req_buf, size_t req_sz, void *resp_buf,
u32 resp_sz, __u64 *fw_err)
static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
struct snp_guest_request_ioctl *rio, u8 type,
void *req_buf, size_t req_sz, void *resp_buf,
u32 resp_sz)
{
u64 seqno;
int rc;
@ -434,7 +437,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
/* Encrypt the userspace provided payload in snp_dev->secret_request. */
rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
rc = enc_payload(snp_dev, seqno, rio->msg_version, type, req_buf, req_sz);
if (rc)
return rc;
@ -445,12 +448,16 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
memcpy(snp_dev->request, &snp_dev->secret_request,
sizeof(snp_dev->secret_request));
rc = __handle_guest_request(snp_dev, exit_code, fw_err);
rc = __handle_guest_request(snp_dev, exit_code, rio);
if (rc) {
if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
if (rc == -EIO &&
rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
return rc;
dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err);
dev_alert(snp_dev->dev,
"Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
rc, rio->exitinfo2);
snp_disable_vmpck(snp_dev);
return rc;
}
@ -490,9 +497,9 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
if (!resp)
return -ENOMEM;
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
resp_len, &arg->fw_err);
resp_len);
if (rc)
goto e_free;
@ -530,9 +537,8 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
return -EFAULT;
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len,
&arg->fw_err);
rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len);
if (rc)
return rc;
@ -592,12 +598,12 @@ cmd:
return -ENOMEM;
snp_dev->input.data_npages = npages;
ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg,
SNP_MSG_REPORT_REQ, &req.data,
sizeof(req.data), resp->data, resp_len, &arg->fw_err);
sizeof(req.data), resp->data, resp_len);
/* If certs length is invalid then copy the returned length */
if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
@ -632,7 +638,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
if (copy_from_user(&input, argp, sizeof(input)))
return -EFAULT;
input.fw_err = 0xff;
input.exitinfo2 = 0xff;
/* Message version must be non-zero */
if (!input.msg_version)
@ -663,7 +669,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
mutex_unlock(&snp_cmd_mutex);
if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
if (input.exitinfo2 && copy_to_user(argp, &input, sizeof(input)))
return -EFAULT;
return ret;

18
include/uapi/linux/sev-guest.h
View File

@ -52,8 +52,14 @@ struct snp_guest_request_ioctl {
__u64 req_data;
__u64 resp_data;
/* firmware error code on failure (see psp-sev.h) */
__u64 fw_err;
/* bits[63:32]: VMM error code, bits[31:0] firmware error code (see psp-sev.h) */
union {
__u64 exitinfo2;
struct {
__u32 fw_error;
__u32 vmm_error;
};
};
};
struct snp_ext_report_req {
@ -77,4 +83,12 @@ struct snp_ext_report_req {
/* Get SNP extended report as defined in the GHCB specification version 2. */
#define SNP_GET_EXT_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x2, struct snp_guest_request_ioctl)
/* Guest message request EXIT_INFO_2 constants */
#define SNP_GUEST_FW_ERR_MASK GENMASK_ULL(31, 0)
#define SNP_GUEST_VMM_ERR_SHIFT 32
#define SNP_GUEST_VMM_ERR(x) (((u64)x) << SNP_GUEST_VMM_ERR_SHIFT)
#define SNP_GUEST_VMM_ERR_INVALID_LEN 1
#define SNP_GUEST_VMM_ERR_BUSY 2
#endif /* __UAPI_LINUX_SEV_GUEST_H_ */