From 77dfb0cf06204509dfe14b013c6bf4705630de54 Mon Sep 17 00:00:00 2001
From: sobomax <sobomax@FreeBSD.org>
Date: Sat, 30 Jan 2016 04:16:05 +0000
Subject: This seems like a very trivial bug that should have been squashed a
 long time ago, but for some reason it was not. Basically, without this change
 dlopen(3)'ing an empty .so file would just cause application to dump core
 with SIGSEGV.

Make sure the file has enough data for at least the ELF header before
mmap'ing it.

Add a test case to check that dlopen an empty file return an error.

There were a separate discussion as to whether it should be SIGBUS
instead when you try to access region mapped from an empty file,
but it's definitely SIGSEGV now, so if anyone want to check that please
be my guest.
Reviewed by:	mjg, cem
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D5112
---
 lib/libc/tests/gen/dlopen_empty_test.c | 97 ++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 lib/libc/tests/gen/dlopen_empty_test.c

(limited to 'lib/libc/tests/gen/dlopen_empty_test.c')

diff --git a/lib/libc/tests/gen/dlopen_empty_test.c b/lib/libc/tests/gen/dlopen_empty_test.c
new file mode 100644
index 0000000..42f9269
--- /dev/null
+++ b/lib/libc/tests/gen/dlopen_empty_test.c
@@ -0,0 +1,97 @@
+/*-
+ * Copyright (c) 2016 Maksym Sobolyev
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/stat.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <atf-c.h>
+
+static const char *funname;
+static char *soname;
+
+static void
+sigsegv_handler(int sig __unused)
+{
+        unlink(soname);
+        free(soname);
+        atf_tc_fail("got SIGSEGV in the %s(3)", funname);
+}
+
+ATF_TC(dlopen_empty_test);
+ATF_TC_HEAD(dlopen_empty_test, tc)
+{
+        atf_tc_set_md_var(tc, "descr", "Tests the dlopen() of an empty file "
+                      "returns an error");
+}
+ATF_TC_BODY(dlopen_empty_test, tc)
+{
+        char tempname[] = "/tmp/temp.XXXXXX";
+        char *fname;
+        int fd;
+        void *dlh;
+        struct sigaction act, oact;
+
+        fname = mktemp(tempname);
+        ATF_REQUIRE_MSG(fname != NULL, "mktemp failed; errno=%d", errno);
+        asprintf(&soname, "%s.so", fname);
+        ATF_REQUIRE_MSG(soname != NULL, "asprintf failed; errno=%d", ENOMEM);
+        fd = open(soname, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
+        ATF_REQUIRE_MSG(fd != -1, "open(\"%s\") failed; errno=%d", soname, errno);
+        close(fd);
+
+        act.sa_handler = sigsegv_handler;
+        act.sa_flags = 0;
+        sigemptyset(&act.sa_mask);
+        ATF_CHECK_MSG(sigaction(SIGSEGV, &act, &oact) != -1,
+            "sigaction() failed");
+
+        funname = "dlopen";
+        dlh = dlopen(soname, RTLD_LAZY);
+        if (dlh != NULL) {
+                funname = "dlclose";
+                dlclose(dlh);
+        }
+        ATF_REQUIRE_MSG(dlh == NULL, "dlopen(\"%s\") did not fail", soname);
+        unlink(soname);
+        free(soname);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+        ATF_TP_ADD_TC(tp, dlopen_empty_test);
+
+        return (atf_no_error());
+}
-- 
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