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

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Message-ID: <20250923172822.GD2547959@ziepe.ca>
Date: Tue, 23 Sep 2025 14:28:22 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Alessandro Zanni <alessandro.zanni87@...il.com>
Cc: kevin.tian@...el.com, shuah@...nel.org, iommu@...ts.linux.dev,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/iommu: prevent use of uninitialized variable

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@...il.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