On 4/1/22 4:08 PM, Daniel Verkamp wrote:
Basic tests to ensure that user/group/other execute bits cannot be
changed after applying F_SEAL_EXEC to a memfd.
Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
---
tools/testing/selftests/memfd/memfd_test.c | 80 ++++++++++++++++++++++
1 file changed, 80 insertions(+)
diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 94df2692e6e4..fdb0e46e9df9 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -28,6 +28,10 @@
#define MFD_DEF_SIZE 8192
#define STACK_SIZE 65536
+#ifndef F_SEAL_EXEC
+#define F_SEAL_EXEC 0x0020
+#endif
+
/*
* Default is not to test hugetlbfs
*/
@@ -594,6 +598,48 @@ static void mfd_fail_grow_write(int fd)
}
}
+static void mfd_assert_mode(int fd, int mode)
+{
+ struct stat st;
+
+ if (fstat(fd, &st) < 0) {
+ printf("fstat(%d) failed: %m\n", fd);
Let's print the filename here - just printing fd isn't useful.
+ abort();
+ } else if ((st.st_mode & 07777) != mode) {
+ printf("wrong file mode 0%04o, but expected 0%04o\n",
+ (int)st.st_mode & 07777, mode);
This one doesn't even print fd - same comment here about filename.
+ abort();
+ }
+}
+
+static void mfd_assert_chmod(int fd, int mode)
+{
+ if (fchmod(fd, mode) < 0) {
+ printf("fchmod(0%04o) failed: %m\n", mode);
Same here.
+ abort();
+ }
+
+ mfd_assert_mode(fd, mode);
+}
+
+static void mfd_fail_chmod(int fd, int mode)
+{
+ struct stat st;
+
+ if (fstat(fd, &st) < 0) {
+ printf("fstat(%d) failed: %m\n", fd);
Same comment about filename
+ abort();
+ }
+
+ if (fchmod(fd, mode) == 0) {
+ printf("fchmod(0%04o) didn't fail as expected\n");
Same comment about filename
+ abort();
+ }
+
+ /* verify that file mode bits did not change */
+ mfd_assert_mode(fd, st.st_mode & 07777);
+}
+
static int idle_thread_fn(void *arg)
{
sigset_t set;
@@ -880,6 +926,39 @@ static void test_seal_resize(void)
close(fd);
}
+/*
+ * Test SEAL_EXEC
+ * Test that chmod() cannot change x bits after sealing
+ */
+static void test_seal_exec(void)
+{
+ int fd;
+
+ printf("%s SEAL-EXEC\n", memfd_str);
+
+ fd = mfd_assert_new("kern_memfd_seal_exec",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+ mfd_assert_mode(fd, 0777);
+
+ mfd_assert_chmod(fd, 0644);
+
+ mfd_assert_has_seals(fd, 0);
+ mfd_assert_add_seals(fd, F_SEAL_EXEC);
+ mfd_assert_has_seals(fd, F_SEAL_EXEC);
+
+ mfd_assert_chmod(fd, 0600);
+ mfd_fail_chmod(fd, 0777);
+ mfd_fail_chmod(fd, 0670);
+ mfd_fail_chmod(fd, 0605);
+ mfd_fail_chmod(fd, 0700);
+ mfd_fail_chmod(fd, 0100);
+ mfd_assert_chmod(fd, 0666);
+
+ close(fd);
+}
+
/*
* Test sharing via dup()
* Test that seals are shared between dupped FDs and they're all equal.
@@ -1059,6 +1138,7 @@ int main(int argc, char **argv)
test_seal_shrink();
test_seal_grow();
test_seal_resize();
+ test_seal_exec();
test_share_dup("SHARE-DUP", "");
test_share_mmap("SHARE-MMAP", "");
The rest looks good.
thanks,
-- Shuah
