Fix a panic in VRB_Cache

This adds error handling for STV_NewObject(.., TRANSIENT) in VRB_Cache,
which would fail when transient is full.

This is a back port of 6045eaaa.

Fixes: #2831

Conflicts:
	bin/varnishd/cache/cache_req_body.c
	bin/varnishtest/tests/r02831.vtc

bin/varnishd/cache/cache_req_body.c

@@ -239,7 +239,12 @@ VRB_Cache(struct req *req, ssize_t maxsize)
 
 	req->body_oc = HSH_Private(req->wrk);
 	AN(req->body_oc);
-	XXXAN(STV_NewObject(req->body_oc, req->wrk, TRANSIENT_STORAGE, 8));
+	if (STV_NewObject(req->body_oc, req->wrk, TRANSIENT_STORAGE, 8) == 0) {
+		(void)VFP_Error(vfc, "Object allocation failed -"
+			" ran out of space in Transient");
+		req->req_body_status = REQ_BODY_FAIL;
+		return (-1);
+	}
 
 	vfc->http = req->http;
 	vfc->oc = req->body_oc;

bin/varnishtest/tests/r02831.vtc

+varnishtest "#2831: Out of storage in cache_req_body"
+
+server s1 {
+	rxreq
+	expect req.url == "/obj1"
+	txresp -bodylen 1048400
+} -start
+
+varnish v1 \
+	-arg "-p nuke_limit=0" \
+	-arg "-sTransient=malloc,1m" \
+	-vcl+backend {
+	import ${vmod_std};
+	sub vcl_recv {
+		if (req.method == "POST") {
+			std.cache_req_body(1KB);
+		}
+	}
+	sub vcl_backend_response {
+		set beresp.do_stream = false;
+		set beresp.storage_hint = "Transient";
+		# Unset Date header to not change the object sizes
+		unset beresp.http.Date;
+	}
+} -start
+
+varnish v1 -cliok "param.set debug +syncvsl"
+
+delay .1
+
+client c1 {
+	# Fill transient
+	txreq -url "/obj1"
+	rxresp
+	expect resp.status == 200
+} -run
+
+delay .1
+
+varnish v1 -expect SMA.Transient.g_bytes > 1048400
+varnish v1 -expect SMA.Transient.g_space < 100
+
+client c1 {
+	# No space for caching this req.body
+	txreq -req "POST" -body "foobar"
+	delay 1
+} -run
+
+varnish v1 -expect SMA.Transient.c_fail == 1
+
+client c1 {
+	# Check that Varnish is still alive
+	txreq -url "/obj1"
+	rxresp
+	expect resp.status == 200
+} -run

doc/changes.rst

+=================================
+Varnish Cache 4.1.11 (unreleased)
+=================================
+
+Changes since 4.1.10:
+
+* New counter added: cache_hit_grace (2831_)
+
+.. _2831: https://github.com/varnishcache/varnish-cache/issues/2831
+
 =================================
 Varnish Cache 4.1.10 (2018-04-25)
 =================================