diff options
Diffstat (limited to 'drivers/virt/coco/sev-guest/sev-guest.c')
-rw-r--r-- | drivers/virt/coco/sev-guest/sev-guest.c | 191 |
1 files changed, 122 insertions, 69 deletions
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index 7b4e9009f335..97dbe715e96a 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -31,6 +31,9 @@ #define AAD_LEN 48 #define MSG_HDR_VER 1 +#define SNP_REQ_MAX_RETRY_DURATION (60*HZ) +#define SNP_REQ_RETRY_DELAY (2*HZ) + struct snp_guest_crypto { struct crypto_aead *tfm; u8 *iv, *authtag; @@ -43,7 +46,15 @@ struct snp_guest_dev { void *certs_data; struct snp_guest_crypto *crypto; + /* request and response are in unencrypted memory */ struct snp_guest_msg *request, *response; + + /* + * Avoid information leakage by double-buffering shared messages + * in fields that are in regular encrypted memory. + */ + struct snp_guest_msg secret_request, secret_response; + struct snp_secrets_page_layout *layout; struct snp_req_data input; u32 *os_area_msg_seqno; @@ -263,14 +274,17 @@ static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg, static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz) { struct snp_guest_crypto *crypto = snp_dev->crypto; - struct snp_guest_msg *resp = snp_dev->response; - struct snp_guest_msg *req = snp_dev->request; + struct snp_guest_msg *resp = &snp_dev->secret_response; + struct snp_guest_msg *req = &snp_dev->secret_request; struct snp_guest_msg_hdr *req_hdr = &req->hdr; struct snp_guest_msg_hdr *resp_hdr = &resp->hdr; dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n", resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz); + /* Copy response from shared memory to encrypted memory. */ + memcpy(resp, snp_dev->response, sizeof(*resp)); + /* Verify that the sequence counter is incremented by 1 */ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1))) return -EBADMSG; @@ -294,7 +308,7 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type, void *payload, size_t sz) { - struct snp_guest_msg *req = snp_dev->request; + struct snp_guest_msg *req = &snp_dev->secret_request; struct snp_guest_msg_hdr *hdr = &req->hdr; memset(req, 0, sizeof(*req)); @@ -318,45 +332,40 @@ 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, 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) { - unsigned long err; - u64 seqno; + unsigned long req_start = jiffies; + unsigned int override_npages = 0; + u64 override_err = 0; int rc; - /* Get message sequence and verify that its a non-zero */ - seqno = snp_get_msg_seqno(snp_dev); - if (!seqno) - return -EIO; - - memset(snp_dev->response, 0, sizeof(struct snp_guest_msg)); - - /* Encrypt the userspace provided payload */ - rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz); - if (rc) - return rc; - +retry_request: /* * Call firmware to process the request. In this function the encrypted * message enters shared memory with the host. So after this call the * 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); - - /* - * If the extended guest request fails due to having too small of a - * certificate data buffer, retry the same guest request without the - * extended data request in order to increment the sequence number - * and thus avoid IV reuse. - */ - if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST && - err == SNP_GUEST_REQ_INVALID_LEN) { - const unsigned int certs_npages = snp_dev->input.data_npages; + rc = snp_issue_guest_request(exit_code, &snp_dev->input, rio); + switch (rc) { + case -ENOSPC: + /* + * If the extended guest request fails due to having too + * small of a certificate data buffer, retry the same + * guest request without the extended data request in + * order to increment the sequence number and thus avoid + * IV reuse. + */ + override_npages = snp_dev->input.data_npages; + exit_code = SVM_VMGEXIT_GUEST_REQUEST; - exit_code = SVM_VMGEXIT_GUEST_REQUEST; + /* + * Override the error to inform callers the given extended + * request buffer size was too small and give the caller the + * required buffer size. + */ + override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN); /* * If this call to the firmware succeeds, the sequence number can @@ -366,15 +375,20 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in * of the VMPCK and the error code being propagated back to the * user as an ioctl() return code. */ - rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err); + goto retry_request; - /* - * Override the error to inform callers the given extended - * request buffer size was too small and give the caller the - * required buffer size. - */ - err = SNP_GUEST_REQ_INVALID_LEN; - snp_dev->input.data_npages = certs_npages; + /* + * 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. + */ + case -EAGAIN: + if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) { + rc = -ETIMEDOUT; + break; + } + schedule_timeout_killable(SNP_REQ_RETRY_DELAY); + goto retry_request; } /* @@ -385,38 +399,75 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in */ snp_inc_msg_seqno(snp_dev); - if (fw_err) - *fw_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; + + return rc; +} + +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; + + /* Get message sequence and verify that its a non-zero */ + seqno = snp_get_msg_seqno(snp_dev); + if (!seqno) + return -EIO; + + /* Clear shared memory's response for the host to populate. */ + 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, rio->msg_version, type, req_buf, req_sz); + if (rc) + return rc; /* - * 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. + * Write the fully encrypted request to the shared unencrypted + * request page. */ - if (!rc && err == SNP_GUEST_REQ_INVALID_LEN) - return -EIO; + memcpy(snp_dev->request, &snp_dev->secret_request, + sizeof(snp_dev->secret_request)); + rc = __handle_guest_request(snp_dev, exit_code, rio); if (rc) { + 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); - goto disable_vmpck; + "Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n", + rc, rio->exitinfo2); + + snp_disable_vmpck(snp_dev); + return rc; } rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz); if (rc) { - dev_alert(snp_dev->dev, - "Detected unexpected decode failure from ASP. rc: %d\n", - rc); - goto disable_vmpck; + dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc); + snp_disable_vmpck(snp_dev); + return rc; } return 0; - -disable_vmpck: - snp_disable_vmpck(snp_dev); - return rc; } static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) @@ -444,9 +495,9 @@ 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; @@ -484,9 +535,8 @@ 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; @@ -546,12 +596,12 @@ 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))) @@ -586,7 +636,7 @@ 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) @@ -617,7 +667,7 @@ 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; @@ -703,6 +753,9 @@ static int __init sev_guest_probe(struct platform_device *pdev) void __iomem *mapping; int ret; + if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + return -ENODEV; + if (!dev->platform_data) return -ENODEV; |