From: Joel Fernandes (Google) <joel@joelfernandes.org>
Date: Wed, 5 Dec 2018 00:13:36 +0000 (+1100)
Subject: selftests/memfd: add tests for F_SEAL_FUTURE_WRITE seal
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=41d81f1707ac61da3a54cfcc9030df2f23608338;p=users%2Fwilly%2Flinux.git

selftests/memfd: add tests for F_SEAL_FUTURE_WRITE seal

Add tests to verify sealing memfds with the F_SEAL_FUTURE_WRITE works as
expected.

Link: http://lkml.kernel.org/r/20181108041537.39694-2-joel@joelfernandes.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Colascione <dancol@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: John Reck <jreck@google.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Lei Yang <Lei.Yang@windriver.com>
Cc: Marc-Andr Lureau <marcandre.lureau@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Todd Kjos <tkjos@google.com>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---

diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 10baa1652fc2..32b207ca7372 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -692,6 +692,79 @@ static void test_seal_write(void)
 	close(fd);
 }
 
+/*
+ * Test SEAL_FUTURE_WRITE
+ * Test whether SEAL_FUTURE_WRITE actually prevents modifications.
+ */
+static void test_seal_future_write(void)
+{
+	int fd;
+	void *p;
+
+	printf("%s SEAL-FUTURE-WRITE\n", memfd_str);
+
+	fd = mfd_assert_new("kern_memfd_seal_future_write",
+			    mfd_def_size,
+			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+	p = mfd_assert_mmap_shared(fd);
+
+	mfd_assert_has_seals(fd, 0);
+	/* Not adding grow/shrink seals makes the future write
+	 * seal fail to get added
+	 */
+	mfd_fail_add_seals(fd, F_SEAL_FUTURE_WRITE);
+
+	mfd_assert_add_seals(fd, F_SEAL_GROW);
+	mfd_assert_has_seals(fd, F_SEAL_GROW);
+
+	/* Should still fail since shrink seal has
+	 * not yet been added
+	 */
+	mfd_fail_add_seals(fd, F_SEAL_FUTURE_WRITE);
+
+	mfd_assert_add_seals(fd, F_SEAL_SHRINK);
+	mfd_assert_has_seals(fd, F_SEAL_GROW |
+				 F_SEAL_SHRINK);
+
+	/* Now should succeed, also verifies that the seal
+	 * could be added with an existing writable mmap
+	 */
+	mfd_assert_add_seals(fd, F_SEAL_FUTURE_WRITE);
+	mfd_assert_has_seals(fd, F_SEAL_SHRINK |
+				 F_SEAL_GROW |
+				 F_SEAL_FUTURE_WRITE);
+
+	/* read should pass, writes should fail */
+	mfd_assert_read(fd);
+	mfd_fail_write(fd);
+
+	munmap(p, mfd_def_size);
+	close(fd);
+
+	/* Test adding all seals (grow, shrink, future write) at once */
+	fd = mfd_assert_new("kern_memfd_seal_future_write2",
+			    mfd_def_size,
+			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+	p = mfd_assert_mmap_shared(fd);
+
+	mfd_assert_has_seals(fd, 0);
+	mfd_assert_add_seals(fd, F_SEAL_SHRINK |
+				 F_SEAL_GROW |
+				 F_SEAL_FUTURE_WRITE);
+	mfd_assert_has_seals(fd, F_SEAL_SHRINK |
+				 F_SEAL_GROW |
+				 F_SEAL_FUTURE_WRITE);
+
+	/* read should pass, writes should fail */
+	mfd_assert_read(fd);
+	mfd_fail_write(fd);
+
+	munmap(p, mfd_def_size);
+	close(fd);
+}
+
 /*
  * Test SEAL_SHRINK
  * Test whether SEAL_SHRINK actually prevents shrinking
@@ -945,6 +1018,7 @@ int main(int argc, char **argv)
 	test_basic();
 
 	test_seal_write();
+	test_seal_future_write();
 	test_seal_shrink();
 	test_seal_grow();
 	test_seal_resize();