async: harden crypto callback poll re-entry

Address review feedback:
- wc_CryptoCb_Poll() now hard-fails (WC_HW_E) when the device is missing
  or unregistered, instead of returning WC_NO_PENDING_E and letting the
  async layer treat an in-flight op as done with an unfilled buffer.
- Poll the callback only while the event is still WC_PENDING_E, so a
  completed result is not overwritten on a later poll pass.
- Include WOLFSSL_ASYNC_CRYPT in the poll guards to match the
  wc_CryptoCb_Poll() declaration.

Author: julek-wolfssl

wolfcrypt/src/async.c

@@ -27,7 +27,8 @@
 #include <wolfssl/error-ssl.h>
 
 #include <wolfssl/wolfcrypt/async.h>
-#if defined(WOLF_CRYPTO_CB) && defined(WOLF_CRYPTO_CB_ASYNC_POLL)
+#if defined(WOLFSSL_ASYNC_CRYPT) && defined(WOLF_CRYPTO_CB) && \
+    defined(WOLF_CRYPTO_CB_ASYNC_POLL)
 #include <wolfssl/wolfcrypt/cryptocb.h>
 #endif
 
@@ -598,10 +599,13 @@ int wolfAsync_EventPoll(WOLF_EVENT* event, WOLF_EVENT_FLAG flags)
         event->ret = wolfAsync_DoSw(asyncDev);
     #endif
 
-    #if defined(WOLF_CRYPTO_CB) && defined(WOLF_CRYPTO_CB_ASYNC_POLL)
-        /* Re-enter the crypto callback to complete the job and fill the
-         * output buffer, like the hardware polls above. */
-        if (asyncDev->cryptocb.devId != INVALID_DEVID) {
+    #if defined(WOLFSSL_ASYNC_CRYPT) && defined(WOLF_CRYPTO_CB) && \
+        defined(WOLF_CRYPTO_CB_ASYNC_POLL)
+        /* Re-enter the crypto callback to complete the job and fill the output
+         * buffer, like the hardware polls above. Poll only while the event is
+         * still pending so a completed result is not overwritten. */
+        if (asyncDev->cryptocb.devId != INVALID_DEVID &&
+            event->ret == WC_NO_ERR_TRACE(WC_PENDING_E)) {
             event->ret = wc_CryptoCb_Poll(asyncDev->cryptocb.devId);
         }
     #endif
@@ -763,13 +767,17 @@ int wolfAsync_EventQueuePoll(WOLF_EVENT_QUEUE* queue, void* context_filter,
                             event->ret = wolfAsync_DoSw(asyncDev);
                         }
                 #elif defined(WOLF_CRYPTO_CB) || defined(HAVE_PK_CALLBACKS)
-                    #if defined(WOLF_CRYPTO_CB) && \
+                    #if defined(WOLFSSL_ASYNC_CRYPT) && \
+                        defined(WOLF_CRYPTO_CB) && \
                         defined(WOLF_CRYPTO_CB_ASYNC_POLL)
                     if (asyncDev->cryptocb.devId != INVALID_DEVID) {
-                        /* Re-enter the crypto callback to complete the job
-                         * and fill the output buffer. */
-                        event->ret =
-                            wc_CryptoCb_Poll(asyncDev->cryptocb.devId);
+                        /* Re-enter the crypto callback to complete the job and
+                         * fill the output buffer. Poll only while still pending
+                         * so a completed result is not overwritten. */
+                        if (event->ret == WC_NO_ERR_TRACE(WC_PENDING_E)) {
+                            event->ret =
+                                wc_CryptoCb_Poll(asyncDev->cryptocb.devId);
+                        }
                     }
                     else
                     #endif

wolfcrypt/src/cryptocb.c

@@ -464,7 +464,10 @@ int wc_CryptoCb_GetDevIdAtIndex(int startIdx)
 /* Returns WC_PENDING_E while in-flight, 0 or an error when done. */
 int wc_CryptoCb_Poll(int devId)
 {
-    int ret = WC_NO_ERR_TRACE(WC_NO_PENDING_E);
+    /* Default hard-fails: a missing or unregistered device cannot complete
+     * the pending job, so never report "no pending" and leave the output
+     * buffer unfilled. */
+    int ret = WC_NO_ERR_TRACE(WC_HW_E);
     CryptoCb* dev = wc_CryptoCb_GetDevice(devId);
     if (dev != NULL && dev->cb != NULL) {
         wc_CryptoInfo info;