Re: [PATCH v8 4/5] iommufd/selftest: Add coverage for IOMMU_GET_HW_INFO ioctl

[Nicolin Chen]

On Thu, Aug 17, 2023 at 07:32:52AM +0000, Tian, Kevin wrote:
> > +TEST_F(iommufd_ioas, get_hw_info)
> > +{
> > +     struct iommu_test_hw_info buffer_exact;
> > +     struct iommu_test_hw_info_buffer {
> > +             struct iommu_test_hw_info info;
> > +             uint64_t trailing_bytes;
> > +     } buffer_larger;
> > +
> > +     if (self->device_id) {
> > +             /* Provide a zero-size user_buffer */
> > +             test_cmd_get_hw_info(self->device_id, NULL, 0);
> > +             /* Provide a user_buffer with exact size */
> > +             test_cmd_get_hw_info(self->device_id, &buffer_exact,
> > sizeof(buffer_exact));
> > +             /*
> > +              * Provide a user_buffer with size larger than the exact size to
> > check if
> > +              * kernel zero the trailing bytes.
> > +              */
> > +             test_cmd_get_hw_info(self->device_id, &buffer_larger,
> > sizeof(buffer_larger));
> 
> Do we also want to test a case where size is smaller than the exact size?

Added one with the following diff:

diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c
index a068bfbe9f83..33d08600be13 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -295,10 +295,13 @@ TEST_F(iommufd_ioas, ioas_area_auto_destroy)
 TEST_F(iommufd_ioas, get_hw_info)
 {
 	struct iommu_test_hw_info buffer_exact;
-	struct iommu_test_hw_info_buffer {
+	struct iommu_test_hw_info_buffer_larger {
 		struct iommu_test_hw_info info;
 		uint64_t trailing_bytes;
 	} buffer_larger;
+	struct iommu_test_hw_info_buffer_smaller {
+		__u32 flags;
+	} buffer_smaller;
 
 	if (self->device_id) {
 		/* Provide a zero-size user_buffer */
@@ -310,6 +313,11 @@ TEST_F(iommufd_ioas, get_hw_info)
 		 * kernel zero the trailing bytes.
 		 */
 		test_cmd_get_hw_info(self->device_id, &buffer_larger, sizeof(buffer_larger));
+		/*
+		 * Provide a user_buffer with size smaller than the exact size to check if
+		 * the fields within the size range still gets updated.
+		 */
+		test_cmd_get_hw_info(self->device_id, &buffer_smaller, sizeof(buffer_smaller));
 	} else {
 		test_err_get_hw_info(ENOENT, self->device_id,
 				     &buffer_exact, sizeof(buffer_exact));
diff --git a/tools/testing/selftests/iommu/iommufd_utils.h b/tools/testing/selftests/iommu/iommufd_utils.h
index 097418f2fdb3..e0753d03ecaa 100644
--- a/tools/testing/selftests/iommu/iommufd_utils.h
+++ b/tools/testing/selftests/iommu/iommufd_utils.h
@@ -21,6 +21,10 @@ static unsigned long BUFFER_SIZE;
 
 static unsigned long PAGE_SIZE;
 
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+#define offsetofend(TYPE, MEMBER) \
+	(offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
+
 /*
  * Have the kernel check the refcount on pages. I don't know why a freshly
  * mmap'd anon non-compound page starts out with a ref of 3
@@ -353,13 +357,13 @@ static void teardown_iommufd(int fd, struct __test_metadata *_metadata)
 static int _test_cmd_get_hw_info(int fd, __u32 device_id,
 				 void *data, size_t data_len)
 {
+	struct iommu_test_hw_info *info = (struct iommu_test_hw_info *)data;
 	struct iommu_hw_info cmd = {
 		.size = sizeof(cmd),
 		.dev_id = device_id,
 		.data_len = data_len,
 		.data_uptr = (uint64_t)data,
 	};
-	struct iommu_test_hw_info *info = (struct iommu_test_hw_info *)data;
 	int ret;
 
 	ret = ioctl(fd, IOMMU_GET_HW_INFO, &cmd);
@@ -389,8 +393,10 @@ static int _test_cmd_get_hw_info(int fd, __u32 device_id,
 	}
 
 	if (info) {
-		assert(info->test_reg == IOMMU_HW_INFO_SELFTEST_REGVAL);
-		assert(!info->flags);
+		if (data_len >= offsetofend(struct iommu_test_hw_info, test_reg))
+			assert(info->test_reg == IOMMU_HW_INFO_SELFTEST_REGVAL);
+		if (data_len >= offsetofend(struct iommu_test_hw_info, flags))
+			assert(!info->flags);
 	}
 
 	return 0;