transfer: refuse POSTFIELDS + RESUME_FROM combo

The code assumes that such a resume is wanting to continue an upload
using the read callback, and since POSTFIELDS is done without callback
libcurl will just misbehave.

This combo will make the transfer fail with CURLE_BAD_FUNCTION_ARGUMENT
with an explanation in the error message.

Reported-by: Smackd0wn on github
Fixes #11081
Closes #11083

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/transfer.c b/lib/transfer.c
index 947070956..d2ff0c24c 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -1325,6 +1325,12 @@ CURLcode Curl_pretransfer(struct Curl_easy *data)
     }
   }
 
+  if(data->set.postfields && data->set.set_resume_from) {
+    /* we can't */
+    failf(data, "cannot mix POSTFIELDS with RESUME_FROM");
+    return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
+
   data->state.prefer_ascii = data->set.prefer_ascii;
   data->state.list_only = data->set.list_only;
   data->state.httpreq = data->set.method;