From: Borislav Petkov (AMD) bp@alien8.de
commit 970ab823743fb54b42002ec76c51481f67436444 upstream.
Return a specific error code - -ENOSPC - to signal the too small cert data buffer instead of checking exit code and exitinfo2.
While at it, hoist the *fw_err assignment in snp_issue_guest_request() so that a proper error value is returned to the callers.
[ Tom: check override_err instead of err. ]
Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Signed-off-by: Tom Lendacky thomas.lendacky@amd.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/r/20230307192449.24732-4-bp@alien8.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/sev.c | 11 ++++--- drivers/virt/coco/sev-guest/sev-guest.c | 48 +++++++++++++++++--------------- 2 files changed, 32 insertions(+), 27 deletions(-)
--- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -2209,15 +2209,16 @@ int snp_issue_guest_request(u64 exit_cod if (ret) goto e_put;
+ *fw_err = ghcb->save.sw_exit_info_2; if (ghcb->save.sw_exit_info_2) { /* Number of expected pages are returned in RBX */ if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST && - ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN) + ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN) { input->data_npages = ghcb_get_rbx(ghcb); - - *fw_err = ghcb->save.sw_exit_info_2; - - ret = -EIO; + ret = -ENOSPC; + } else { + ret = -EIO; + } }
e_put: --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -322,7 +322,8 @@ static int handle_guest_request(struct s u8 type, void *req_buf, size_t req_sz, void *resp_buf, u32 resp_sz, __u64 *fw_err) { - unsigned long err; + unsigned long err, override_err = 0; + unsigned int override_npages = 0; u64 seqno; int rc;
@@ -338,6 +339,7 @@ static int handle_guest_request(struct s 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 @@ -346,17 +348,24 @@ static int handle_guest_request(struct s */ 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; + 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_REQ_INVALID_LEN;
/* * If this call to the firmware succeeds, the sequence number can @@ -366,15 +375,7 @@ static int handle_guest_request(struct s * 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); - - /* - * 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; + goto retry_request; }
/* @@ -386,7 +387,10 @@ static int handle_guest_request(struct s snp_inc_msg_seqno(snp_dev);
if (fw_err) - *fw_err = err; + *fw_err = override_err ?: err; + + if (override_npages) + snp_dev->input.data_npages = override_npages;
/* * If an extended guest request was issued and the supplied certificate @@ -394,7 +398,7 @@ static int handle_guest_request(struct s * prevent IV reuse. If the standard request was successful, return -EIO * back to the caller as would have originally been returned. */ - if (!rc && err == SNP_GUEST_REQ_INVALID_LEN) + if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN) return -EIO;
if (rc) {