http: don't set the "rewind" flag when not uploading anything

It triggers an assert.

Detected by OSS-Fuzz
Bug: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=8144
Closes #2546

diff --git a/lib/http.c b/lib/http.c
index ec709ff8d32ab41e5808e3597160b0cc44f84546..1a313b4fbec46f1c45671b42d8b9263ad0c53abc 100644 (file)
--- a/lib/http.c
+++ b/lib/http.c
@@ -433,7 +433,7 @@ static CURLcode http_perhapsrewind(struct connectdata *conn)
            data left to send, keep on sending. */
 
         /* rewind data when completely done sending! */
-        if(!conn->bits.authneg) {
+        if(!conn->bits.authneg && (conn->writesockfd != CURL_SOCKET_BAD)) {
           conn->bits.rewindaftersend = TRUE;
           infof(data, "Rewind stream after send\n");
         }