[v4,2/2] selftests/memfd: Add tests for F_SEAL_FUTURE_WRITE seal

Commit Message

Joel Fernandes Jan. 12, 2019, 8:38 p.m. UTC

From: "Joel Fernandes (Google)" <[e-mail]>

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

Cc: [e-mail]
Cc: [e-mail]
Cc: Jann Horn <[e-mail]>
Cc: John Stultz <[e-mail]>
Signed-off-by: Joel Fernandes (Google) <[e-mail]>
---
 tools/testing/selftests/memfd/memfd_test.c | 74 ++++++++++++++++++++++
 1 file changed, 74 insertions(+)

Comments

Shuah Jan. 15, 2019, 1:39 a.m. UTC | #1

On 1/12/19 1:38 PM, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <[e-mail]>
> 
> Add tests to verify sealing memfds with the F_SEAL_FUTURE_WRITE works as
> expected.
> 
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: Jann Horn <[e-mail]>
> Cc: John Stultz <[e-mail]>
> Signed-off-by: Joel Fernandes (Google) <[e-mail]>
> ---

Looks good to me. For selftest part of the series:

Reviewed-by: Shuah Khan <[e-mail]>

thanks,
-- Shuah

Joel Fernandes Jan. 15, 2019, 2:50 p.m. UTC | #2

On Mon, Jan 14, 2019 at 06:39:59PM -0700, shuah wrote:
> On 1/12/19 1:38 PM, Joel Fernandes wrote:
> > From: "Joel Fernandes (Google)" <[e-mail]>
> > 
> > Add tests to verify sealing memfds with the F_SEAL_FUTURE_WRITE works as
> > expected.
> > 
> > Cc: [e-mail]
> > Cc: [e-mail]
> > Cc: Jann Horn <[e-mail]>
> > Cc: John Stultz <[e-mail]>
> > Signed-off-by: Joel Fernandes (Google) <[e-mail]>
> > ---
> 
> Looks good to me. For selftest part of the series:
> 
> Reviewed-by: Shuah Khan <[e-mail]>

Thanks!

John, could you provide your Reviewed-by again for patch 1/2 ? I had dropped
it since the patch had some more changes.

thanks,

 - Joel

Patch

diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 10baa1652fc2..c67d32eeb668 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -54,6 +54,22 @@  static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
 	return fd;
 }
 
+static int mfd_assert_reopen_fd(int fd_in)
+{
+	int r, fd;
+	char path[100];
+
+	sprintf(path, "/proc/self/fd/%d", fd_in);
+
+	fd = open(path, O_RDWR);
+	if (fd < 0) {
+		printf("re-open of existing fd %d failed\n", fd_in);
+		abort();
+	}
+
+	return fd;
+}
+
 static void mfd_fail_new(const char *name, unsigned int flags)
 {
 	int r;
@@ -255,6 +271,25 @@  static void mfd_assert_read(int fd)
 	munmap(p, mfd_def_size);
 }
 
+/* Test that PROT_READ + MAP_SHARED mappings work. */
+static void mfd_assert_read_shared(int fd)
+{
+	void *p;
+
+	/* verify PROT_READ and MAP_SHARED *is* allowed */
+	p = mmap(NULL,
+		 mfd_def_size,
+		 PROT_READ,
+		 MAP_SHARED,
+		 fd,
+		 0);
+	if (p == MAP_FAILED) {
+		printf("mmap() failed: %m\n");
+		abort();
+	}
+	munmap(p, mfd_def_size);
+}
+
 static void mfd_assert_write(int fd)
 {
 	ssize_t l;
@@ -692,6 +727,44 @@  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, fd2;
+	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);
+
+	mfd_assert_add_seals(fd, F_SEAL_FUTURE_WRITE);
+	mfd_assert_has_seals(fd, F_SEAL_FUTURE_WRITE);
+
+	/* read should pass, writes should fail */
+	mfd_assert_read(fd);
+	mfd_assert_read_shared(fd);
+	mfd_fail_write(fd);
+
+	fd2 = mfd_assert_reopen_fd(fd);
+	/* read should pass, writes should still fail */
+	mfd_assert_read(fd2);
+	mfd_assert_read_shared(fd2);
+	mfd_fail_write(fd2);
+
+	munmap(p, mfd_def_size);
+	close(fd2);
+	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();