[master] 1678f98fa cache_fetch: Fail if storage allocation for synthetic body fails

[Nils Goroll]

commit 1678f98fab599100ebee57328774da9ad8f96460
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Fri Apr 11 14:07:51 2025 +0200

    cache_fetch: Fail if storage allocation for synthetic body fails
    
    Fixes #4313

diff --git a/bin/varnishd/cache/cache_fetch.c b/bin/varnishd/cache/cache_fetch.c
index 2f67446b6..f5a1a1d6a 100644
--- a/bin/varnishd/cache/cache_fetch.c
+++ b/bin/varnishd/cache/cache_fetch.c
@@ -1020,14 +1020,17 @@ vbf_stp_error(struct worker *wrk, struct busyobj *bo)
 	o = 0;
 	while (ll > 0) {
 		l = ll;
-		if (VFP_GetStorage(bo->vfc, &l, &ptr) != VFP_OK)
-			break;
+		if (VFP_GetStorage(bo->vfc, &l, &ptr) != VFP_OK) {
+			VSB_destroy(&synth_body);
+			return (F_STP_FAIL);
+		}
 		l = vmin(l, ll);
 		memcpy(ptr, VSB_data(synth_body) + o, l);
 		VFP_Extend(bo->vfc, l, l == ll ? VFP_END : VFP_OK);
 		ll -= l;
 		o += l;
 	}
+	assert(o == VSB_len(synth_body));
 	AZ(ObjSetU64(wrk, oc, OA_LEN, o));
 	VSB_destroy(&synth_body);
 	ObjSetState(wrk, oc, BOS_PREP_STREAM);
diff --git a/bin/varnishtest/tests/r04313.vtc b/bin/varnishtest/tests/r04313.vtc
new file mode 100644
index 000000000..3a43deff9
--- /dev/null
+++ b/bin/varnishtest/tests/r04313.vtc
@@ -0,0 +1,43 @@
+varnishtest "storage failure with synthetic body"
+
+varnish v1 -arg "-sTransient=debug,maxspace=32B" -vcl {
+	backend none none;
+
+	sub vcl_recv {
+		return(pass);
+	}
+
+	# avoid the client side running into the same storage failure
+	sub vcl_synth {
+		set resp.body = resp.reason;
+		return(deliver);
+	}
+
+	sub vcl_recv {
+		return(pass);
+	}
+
+	sub vcl_backend_error {
+		set beresp.status = 200;
+		set beresp.body =
+			"0123456789abcdef" +
+			"0123456789abcdef" +
+			"X";
+		return (deliver);
+	}
+} -start
+
+logexpect l1 -v v1 -q "vxid == 1002" {
+	fail add *	End
+	expect * * Storage	{^-sdebug: max_size=32 reached}
+	expect 0 = FetchError	{^Could not get storage}
+	fail clear
+} -start
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 503
+} -run
+
+logexpect l1 -wait