[PATCH] iommufd/selftest: Return dmabuf fd from IOMMU_TEST_OP_DMABUF_GET again

[Qinyun Tan <qinyuntan@linux.alibaba.com>]

The selftest helper reads the new dmabuf fd from the ioctl return
value:

	*out_fd = ioctl(fd, IOMMU_TEST_CMD, &cmd);

Commit dba4254e216d ("iommufd/selftest: Fix dmabuf leak in
iommufd_test_dmabuf_get()") fixed the dmabuf leak on dma_buf_fd()
failure, but the applied version also changed the success path to
return 0, so userspace no longer receives the fd.  Note the patch as
posted on the list returned rc here; the change to return 0 appeared
when it was applied:

  https://lore.kernel.org/all/20260707030635.221577-1-seven.yi.lee@gmail.com/

Every test using test_cmd_get_dmabuf() then operates on fd 0 instead
of the dmabuf, and the dmabuf_simple and dmabuf_revoke selftests fail
across all fixtures:

  # iommufd.c:1595:dmabuf_simple:Expected -1 (-1) ==
    _test_ioctl_ioas_map_file(...) (0)

Keep the dma_buf_put() on failure but return the fd on success.

Fixes: dba4254e216d ("iommufd/selftest: Fix dmabuf leak in iommufd_test_dmabuf_get()")
Signed-off-by: Qinyun Tan <qinyuntan@linux.alibaba.com>
---
 drivers/iommu/iommufd/selftest.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index ee706f18f7e91..f6da927461b57 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -2056,11 +2056,9 @@ static int iommufd_test_dmabuf_get(struct iommufd_ucmd *ucmd,
 	}
 
 	rc = dma_buf_fd(dmabuf, open_flags);
-	if (rc < 0) {
+	if (rc < 0)
 		dma_buf_put(dmabuf);
-		return rc;
-	}
-	return 0;
+	return rc;
 
 err_free:
 	kfree(priv->memory);
-- 
2.43.7