[4.1] a9e6766 Add an assert preventing buffer overflows

[Martin Blix Grydeland]

commit a9e67666349b5654102621281022464408fe8df8
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Mon Nov 28 11:56:49 2016 +0100

    Add an assert preventing buffer overflows
    
    Make sure that the workspace can accomodate the pipelined data before
    memmoving it into place in SES_RxReInit.

diff --git a/bin/varnishd/cache/cache_session.c b/bin/varnishd/cache/cache_session.c
index 0e2a746..6c5930b 100644
--- a/bin/varnishd/cache/cache_session.c
+++ b/bin/varnishd/cache/cache_session.c
@@ -177,6 +177,7 @@ SES_RxReInit(struct http_conn *htc)
 	if (htc->pipeline_b != NULL) {
 		l = htc->pipeline_e - htc->pipeline_b;
 		assert(l > 0);
+		assert(l <= htc->ws->r - htc->rxbuf_b);
 		memmove(htc->rxbuf_b, htc->pipeline_b, l);
 		htc->rxbuf_e += l;
 		htc->pipeline_b = NULL;