selftest for default_file_splice_read() infoleak

bug fixed in commit b9dc6f65 ("fix a fencepost error in pipe_advance()")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

tools/testing/selftests/Makefile

@@ -24,6 +24,7 @@ TARGETS += ptrace
 TARGETS += seccomp
 TARGETS += sigaltstack
 TARGETS += size
+TARGETS += splice
 TARGETS += static_keys
 TARGETS += sync
 TARGETS += sysctl

tools/testing/selftests/splice/Makefile

+TEST_PROGS := default_file_splice_read.sh
+EXTRA := default_file_splice_read
+all: $(TEST_PROGS) $(EXTRA)
+
+include ../lib.mk
+
+clean:
+	rm -fr $(TEST_PROGS) $(EXTRA)

tools/testing/selftests/splice/default_file_splice_read.c

+#define _GNU_SOURCE
+#include <fcntl.h>
+
+int main(int argc, char **argv)
+{
+        splice(0, 0, 1, 0, 1<<30, 0);
+	return 0;
+}

tools/testing/selftests/splice/default_file_splice_read.sh

+#!/bin/sh
+n=`./default_file_splice_read </dev/null | wc -c`
+
+test "$n" = 0 && exit 0
+
+echo "default_file_splice_read broken: leaked $n"
+exit 1