[PATCH] selftests/iommu: prevent use of uninitialized variable

[PATCH] selftests/iommu: prevent use of uninitialized variable

[Alessandro Zanni]

Fix to avoid the usage of the `res` variable uninitialized in the
following macro expansions.

It solves the following warning:
In function ‘iommufd_viommu_vdevice_alloc’,
  inlined from ‘wrapper_iommufd_viommu_vdevice_alloc’ at
iommufd.c:2889:1:
../kselftest_harness.h:760:12: warning: ‘ret’ may be used uninitialized
[-Wmaybe-uninitialized]
  760 |   if (!(__exp _t __seen)) { \
      |      ^
../kselftest_harness.h:513:9: note: in expansion of macro ‘__EXPECT’
  513 |   __EXPECT(expected, #expected, seen, #seen, ==, 1)
      |   ^~~~~~~~
iommufd_utils.h:1057:9: note: in expansion of macro ‘ASSERT_EQ’
 1057 |   ASSERT_EQ(0, _test_cmd_trigger_vevents(self->fd, dev_id,
nvevents))
      |   ^~~~~~~~~
iommufd.c:2924:17: note: in expansion of macro
‘test_cmd_trigger_vevents’
 2924 |   test_cmd_trigger_vevents(dev_id, 3);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~

The issue can be reproduced, building the tests, with the command:
make -C tools/testing/selftests TARGETS=iommu

Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
---
 tools/testing/selftests/iommu/iommufd_utils.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/iommu/iommufd_utils.h b/tools/testing/selftests/iommu/iommufd_utils.h
index 3c3e08b8c90e..4ae0fcc4f871 100644
--- a/tools/testing/selftests/iommu/iommufd_utils.h
+++ b/tools/testing/selftests/iommu/iommufd_utils.h
@@ -1042,7 +1042,7 @@ static int _test_cmd_trigger_vevents(int fd, __u32 dev_id, __u32 nvevents)
 			.dev_id = dev_id,
 		},
 	};
-	int ret;
+	int ret = 0;
 
 	while (nvevents--) {
 		ret = ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
-- 
2.43.0

Re: [PATCH] selftests/iommu: prevent use of uninitialized variable

[Jason Gunthorpe]

On Tue, Sep 23, 2025 at 05:01:06PM +0200, Alessandro Zanni wrote:
> Fix to avoid the usage of the `res` variable uninitialized in the
> following macro expansions.
> 
> It solves the following warning:
> In function ‘iommufd_viommu_vdevice_alloc’,
>   inlined from ‘wrapper_iommufd_viommu_vdevice_alloc’ at
> iommufd.c:2889:1:
> ../kselftest_harness.h:760:12: warning: ‘ret’ may be used uninitialized
> [-Wmaybe-uninitialized]
>   760 |   if (!(__exp _t __seen)) { \
>       |      ^
> ../kselftest_harness.h:513:9: note: in expansion of macro ‘__EXPECT’
>   513 |   __EXPECT(expected, #expected, seen, #seen, ==, 1)
>       |   ^~~~~~~~
> iommufd_utils.h:1057:9: note: in expansion of macro ‘ASSERT_EQ’
>  1057 |   ASSERT_EQ(0, _test_cmd_trigger_vevents(self->fd, dev_id,
> nvevents))
>       |   ^~~~~~~~~
> iommufd.c:2924:17: note: in expansion of macro
> ‘test_cmd_trigger_vevents’
>  2924 |   test_cmd_trigger_vevents(dev_id, 3);
>       |   ^~~~~~~~~~~~~~~~~~~~~~~~
> 
> The issue can be reproduced, building the tests, with the command:
> make -C tools/testing/selftests TARGETS=iommu
> 
> Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
> ---
>  tools/testing/selftests/iommu/iommufd_utils.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

I think it should be like this?

@@ -1042,15 +1042,12 @@ static int _test_cmd_trigger_vevents(int fd, __u32 dev_id, __u32 nvevents)
                        .dev_id = dev_id,
                },
        };
-       int ret;
 
-       while (nvevents--) {
-               ret = ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
-                           &trigger_vevent_cmd);
-               if (ret < 0)
+       while (nvevents--)
+               if (ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
+                         &trigger_vevent_cmd))
                        return -1;
-       }
-       return ret;
+       return 0;
 }

And add a fixes line?

Jason

Re: [PATCH] selftests/iommu: prevent use of uninitialized variable

[Alessandro Zanni]

On Tue, Sep 23, 2025 at 02:28:22PM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 23, 2025 at 05:01:06PM +0200, Alessandro Zanni wrote:
> > Fix to avoid the usage of the `res` variable uninitialized in the
> > following macro expansions.
> > 
> > It solves the following warning:
> > In function ‘iommufd_viommu_vdevice_alloc’,
> >   inlined from ‘wrapper_iommufd_viommu_vdevice_alloc’ at
> > iommufd.c:2889:1:
> > ../kselftest_harness.h:760:12: warning: ‘ret’ may be used uninitialized
> > [-Wmaybe-uninitialized]
> >   760 |   if (!(__exp _t __seen)) { \
> >       |      ^
> > ../kselftest_harness.h:513:9: note: in expansion of macro ‘__EXPECT’
> >   513 |   __EXPECT(expected, #expected, seen, #seen, ==, 1)
> >       |   ^~~~~~~~
> > iommufd_utils.h:1057:9: note: in expansion of macro ‘ASSERT_EQ’
> >  1057 |   ASSERT_EQ(0, _test_cmd_trigger_vevents(self->fd, dev_id,
> > nvevents))
> >       |   ^~~~~~~~~
> > iommufd.c:2924:17: note: in expansion of macro
> > ‘test_cmd_trigger_vevents’
> >  2924 |   test_cmd_trigger_vevents(dev_id, 3);
> >       |   ^~~~~~~~~~~~~~~~~~~~~~~~
> > 
> > The issue can be reproduced, building the tests, with the command:
> > make -C tools/testing/selftests TARGETS=iommu
> > 
> > Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
> > ---
> >  tools/testing/selftests/iommu/iommufd_utils.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> I think it should be like this?
> 
> @@ -1042,15 +1042,12 @@ static int _test_cmd_trigger_vevents(int fd, __u32 dev_id, __u32 nvevents)
>                         .dev_id = dev_id,
>                 },
>         };
> -       int ret;
>  
> -       while (nvevents--) {
> -               ret = ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
> -                           &trigger_vevent_cmd);
> -               if (ret < 0)
> +       while (nvevents--)
> +               if (ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
> +                         &trigger_vevent_cmd))
>                         return -1;
> -       }
> -       return ret;
> +       return 0;
>  }
> 
> And add a fixes line?
> 
> Jason

Thank you for the reply.
I'm not sure the right behavior the test should have:
- in the version you proposed, when ioctl() returns a positive
value the loop ends and the next tests are skipped.
- in the original version, if the function ioctl() returns a
positive value the loop continues with the following tests.

Which one is the desired behavior?

Thanks,
Alessandro

Re: [PATCH] selftests/iommu: prevent use of uninitialized variable

[Jason Gunthorpe]

On Tue, Sep 23, 2025 at 11:38:13PM +0200, Alessandro Zanni wrote:
> On Tue, Sep 23, 2025 at 02:28:22PM -0300, Jason Gunthorpe wrote:
> > On Tue, Sep 23, 2025 at 05:01:06PM +0200, Alessandro Zanni wrote:
> > > Fix to avoid the usage of the `res` variable uninitialized in the
> > > following macro expansions.
> > > 
> > > It solves the following warning:
> > > In function ‘iommufd_viommu_vdevice_alloc’,
> > >   inlined from ‘wrapper_iommufd_viommu_vdevice_alloc’ at
> > > iommufd.c:2889:1:
> > > ../kselftest_harness.h:760:12: warning: ‘ret’ may be used uninitialized
> > > [-Wmaybe-uninitialized]
> > >   760 |   if (!(__exp _t __seen)) { \
> > >       |      ^
> > > ../kselftest_harness.h:513:9: note: in expansion of macro ‘__EXPECT’
> > >   513 |   __EXPECT(expected, #expected, seen, #seen, ==, 1)
> > >       |   ^~~~~~~~
> > > iommufd_utils.h:1057:9: note: in expansion of macro ‘ASSERT_EQ’
> > >  1057 |   ASSERT_EQ(0, _test_cmd_trigger_vevents(self->fd, dev_id,
> > > nvevents))
> > >       |   ^~~~~~~~~
> > > iommufd.c:2924:17: note: in expansion of macro
> > > ‘test_cmd_trigger_vevents’
> > >  2924 |   test_cmd_trigger_vevents(dev_id, 3);
> > >       |   ^~~~~~~~~~~~~~~~~~~~~~~~
> > > 
> > > The issue can be reproduced, building the tests, with the command:
> > > make -C tools/testing/selftests TARGETS=iommu
> > > 
> > > Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
> > > ---
> > >  tools/testing/selftests/iommu/iommufd_utils.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > I think it should be like this?
> > 
> > @@ -1042,15 +1042,12 @@ static int _test_cmd_trigger_vevents(int fd, __u32 dev_id, __u32 nvevents)
> >                         .dev_id = dev_id,
> >                 },
> >         };
> > -       int ret;
> >  
> > -       while (nvevents--) {
> > -               ret = ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
> > -                           &trigger_vevent_cmd);
> > -               if (ret < 0)
> > +       while (nvevents--)
> > +               if (ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
> > +                         &trigger_vevent_cmd))
> >                         return -1;
> > -       }
> > -       return ret;
> > +       return 0;
> >  }
> > 
> > And add a fixes line?
> > 
> > Jason
> 
> Thank you for the reply.
> I'm not sure the right behavior the test should have:
> - in the version you proposed, when ioctl() returns a positive
> value the loop ends and the next tests are skipped.
> - in the original version, if the function ioctl() returns a
> positive value the loop continues with the following tests.
> 
> Which one is the desired behavior?

Sorry it should be !ioctl()

The ioctl will only return 0 or -errno

Jason