linux-kernel - [PATCH 4/4] selftests/memfd: add tests for MFD

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Message-Id: <20220729061504.744140-2-jeffxu@google.com>
Date:   Fri, 29 Jul 2022 06:15:04 +0000
From:   Jeff Xu <jeffxu@...gle.com>
To:     skhan@...uxfoundation.org
Cc:     akpm@...ux-foundation.org, dmitry.torokhov@...il.com,
        dverkamp@...omium.org, hughd@...gle.com, jeffxu@...gle.com,
        jorgelo@...omium.org, keescook@...omium.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-mm@...ck.org, mnissler@...omium.org
Subject: [PATCH 4/4] selftests/memfd: add tests for MFD_NOEXEC

From: Daniel Verkamp <dverkamp@...omium.org>

Tests that ensure MFD_NOEXEC memfds have the appropriate mode bits and
cannot be chmod-ed into being executable.

Co-developed-by: Jeff Xu <jeffxu@...gle.com>
Signed-off-by: Jeff Xu <jeffxu@...gle.com>
Signed-off-by: Daniel Verkamp <dverkamp@...omium.org>
---
 tools/testing/selftests/memfd/memfd_test.c | 34 ++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 1d7e7b36bbdd..4906f778564e 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -36,6 +36,10 @@
 #define MAX_PATH 256
 #endif
 
+#ifndef MFD_NOEXEC
+#define MFD_NOEXEC	0x0008U
+#endif
+
 /*
  * Default is not to test hugetlbfs
  */
@@ -1006,6 +1010,35 @@ static void test_seal_exec(void)
 	close(fd);
 }
 
+/*
+ * Test memfd_create with MFD_NOEXEC flag
+ * Test that MFD_NOEXEC applies F_SEAL_EXEC and prevents change of exec bits
+ */
+static void test_noexec(void)
+{
+	int fd;
+
+	printf("%s NOEXEC\n", memfd_str);
+
+	/* Create with NOEXEC and ALLOW_SEALING */
+	fd = mfd_assert_new("kern_memfd_noexec",
+			    mfd_def_size,
+			    MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC);
+	mfd_assert_mode(fd, 0666);
+	mfd_assert_has_seals(fd, F_SEAL_EXEC);
+	mfd_fail_chmod(fd, 0777);
+	close(fd);
+
+	/* Create with NOEXEC but without ALLOW_SEALING */
+	fd = mfd_assert_new("kern_memfd_noexec",
+			    mfd_def_size,
+			    MFD_CLOEXEC | MFD_NOEXEC);
+	mfd_assert_mode(fd, 0666);
+	mfd_assert_has_seals(fd, F_SEAL_EXEC | F_SEAL_SEAL);
+	mfd_fail_chmod(fd, 0777);
+	close(fd);
+}
+
 /*
  * Test sharing via dup()
  * Test that seals are shared between dupped FDs and they're all equal.
@@ -1179,6 +1212,7 @@ int main(int argc, char **argv)
 
 	test_create();
 	test_basic();
+	test_noexec();
 
 	test_seal_write();
 	test_seal_future_write();
-- 
2.37.1.455.g008518b4e5-goog