[PATCH 09/10] hw/tpm: crb: Consider response_buffer->len of received response

[Stefan Berger <stefanb@linux.ibm.com>]

When the CRB receives a TPM reponse from the backend, then reject responses
that are shorter than the TPM_HEADER_SIZE. When determining the size of the
reponse, also consider the length of the response_buffer as being possibly
shorter than the negotiated backend buffer size or the size indicated in
the response itself.

Fixes: 2a660ad67d15 ("hw/tpm: Implement TPM CRB chunking logic")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 hw/tpm/tpm_crb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/tpm/tpm_crb.c b/hw/tpm/tpm_crb.c
index 4bd1919952..6ae2261b43 100644
--- a/hw/tpm/tpm_crb.c
+++ b/hw/tpm/tpm_crb.c
@@ -325,13 +325,15 @@ static void tpm_crb_request_completed(TPMIf *ti, int ret)
     CRBState *s = CRB(ti);
 
     ARRAY_FIELD_DP32(s->regs, CRB_CTRL_START, Start, 0);
-    if (ret != 0) {
+    if (ret != 0 || s->response_buffer->len < TPM_HEADER_SIZE) {
         ARRAY_FIELD_DP32(s->regs, CRB_CTRL_STS,
                          tpmSts, 1); /* fatal error */
         tpm_crb_clear_internal_buffers(s);
     } else {
         uint32_t actual_resp_size = tpm_cmd_get_size(s->response_buffer->data);
         uint32_t total_resp_size = MIN(actual_resp_size, s->be_buffer_size);
+
+        total_resp_size = MIN(total_resp_size, s->response_buffer->len);
         g_byte_array_set_size(s->response_buffer, total_resp_size);
         s->response_offset = 0;
     }
-- 
2.55.0