Addressed comments

apps/wolfsshd/wolfsshd.c

@@ -3028,6 +3028,23 @@ static char* _convertHelper(WCHAR* in, void* heap) {
     return ret;
 }
 
+/* free the argv/cmdArgs buffers built from the wide command line. Safe to
+ * call on partially initialized state: NULL argv or cmdArgs is ignored. */
+static void _freeWinArgs(char** argv, DWORD argc, LPWSTR* cmdArgs)
+{
+    DWORD z;
+
+    if (argv != NULL) {
+        for (z = 0; z < argc; z++) {
+            WFREE(argv[z], NULL, DYNTYPE_SSHD);
+        }
+        WFREE(argv, NULL, DYNTYPE_SSHD);
+    }
+    if (cmdArgs != NULL) {
+        LocalFree(cmdArgs);
+    }
+}
+
 static void StartSSHD(DWORD argc, LPTSTR* wargv)
 #else
 static int StartSSHD(int argc, char** argv)
@@ -3178,6 +3195,7 @@ static int StartSSHD(int argc, char** argv)
             #ifndef _WIN32
             return WS_FATAL_ERROR;
             #else
+            _freeWinArgs(argv, argc, cmdArgs);
             return;
             #endif
         #endif
@@ -3191,6 +3209,7 @@ static int StartSSHD(int argc, char** argv)
         #ifndef _WIN32
             return WS_SUCCESS;
         #else
+            _freeWinArgs(argv, argc, cmdArgs);
             return;
         #endif
 
@@ -3199,6 +3218,7 @@ static int StartSSHD(int argc, char** argv)
         #ifndef _WIN32
             return WS_SUCCESS;
         #else
+            _freeWinArgs(argv, argc, cmdArgs);
             return;
         #endif
         }
@@ -3331,12 +3351,10 @@ static int StartSSHD(int argc, char** argv)
                 if (SetServiceStatus(serviceStatusHandle, &serviceStatus) == FALSE) {
                     wolfSSH_Log(WS_LOG_ERROR, "[SSHD] Issue updating service status");
                 }
+                _freeWinArgs(argv, argc, cmdArgs);
                 return;
             }
         }
-        if (cmdArgs != NULL) {
-            LocalFree(cmdArgs);
-        }
     }
 #endif
 
@@ -3517,13 +3535,11 @@ static int StartSSHD(int argc, char** argv)
     }
 
 #ifdef _WIN32
-    if (isDaemon) { /* free up temporary memory used for conversion of args from wchar_t */
-        unsigned int z;
-        for (z = 0; z < argc; z++) {
-            WFREE(argv[z], NULL, DYNTYPE_SSHD);
-        }
-        WFREE(argv, NULL, DYNTYPE_SSHD);
-    }
+    /* free up temporary memory used for conversion of args from wchar_t.
+     * Not gated on isDaemon: argv/cmdArgs are allocated in both daemon and
+     * -D modes. _freeWinArgs() tolerates NULL argv/cmdArgs from an early
+     * failure, and argc tracks argv's length once it is allocated. */
+    _freeWinArgs(argv, argc, cmdArgs);
 #else
     return 0;
 #endif

src/wolfsftp.c

@@ -4385,7 +4385,6 @@ int wolfSSH_SFTP_RecvWrite(WOLFSSH* ssh, int reqId, byte* data, word32 maxSz)
     OVERLAPPED offset;
     HANDLE fd;
     DWORD bytesWritten;
-    LARGE_INTEGER fileSize;
     int ret = WS_SUCCESS;
     int rc;
     int isAppend = 0;
@@ -4455,19 +4454,16 @@ int wolfSSH_SFTP_RecvWrite(WOLFSSH* ssh, int reqId, byte* data, word32 maxSz)
 
         /* WOLFSSH_FXF_APPEND was requested at open: FILE_APPEND_DATA alone
          * does not force writes to EOF once the handle also carries
-         * FILE_WRITE_DATA (granted implicitly by GENERIC_WRITE), so the
-         * client-supplied offset must be overridden with the current EOF. */
+         * FILE_WRITE_DATA (granted implicitly by GENERIC_WRITE). Resolving
+         * EOF ourselves with GetFileSizeEx() and writing at that offset is a
+         * non-atomic read-modify-write: the file is shared FILE_SHARE_WRITE,
+         * so concurrent appenders would resolve the same offset and overwrite
+         * each other. Setting both OVERLAPPED offset fields to 0xFFFFFFFF
+         * tells WriteFile() to append atomically at end of file, matching the
+         * POSIX O_APPEND path. */
         if (isAppend) {
-            if (GetFileSizeEx(fd, &fileSize) == 0) {
-                WLOG(WS_LOG_SFTP, "Error getting file size for append");
-                res  = err;
-                type = WOLFSSH_FTP_FAILURE;
-                ret  = WS_INVALID_STATE_E;
-            }
-            else {
-                offset.Offset     = fileSize.LowPart;
-                offset.OffsetHigh = (DWORD)fileSize.HighPart;
-            }
+            offset.Offset     = 0xFFFFFFFF;
+            offset.OffsetHigh = 0xFFFFFFFF;
         }
     }