[PATCH] drm/imagination: Fixed oops when misusing ioctl CREATE_HWRT_DATASET

[Donald Robson]

While writing the matching IGT suite I discovered that it's possible to
cause a kernel oops when using DRM_IOCTL_PVR_CREATE_HWRT_DATASET when
the call to hwrt_init_common_fw_structure() fails.

Use an unwind-type error path to avoid cleaning up the object using the
the release function before it is fully resolved.

Signed-off-by: Donald Robson <donald.rob...@imgtec.com>
---
 drivers/gpu/drm/imagination/pvr_hwrt.c | 27 +++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_hwrt.c 
b/drivers/gpu/drm/imagination/pvr_hwrt.c
index c4213c18489e..54f88d6c01e5 100644
--- a/drivers/gpu/drm/imagination/pvr_hwrt.c
+++ b/drivers/gpu/drm/imagination/pvr_hwrt.c
@@ -458,7 +458,7 @@ pvr_hwrt_dataset_create(struct pvr_file *pvr_file,
                        struct drm_pvr_ioctl_create_hwrt_dataset_args *args)
 {
        struct pvr_hwrt_dataset *hwrt;
-       int err;
+       int err, i = 0;
 
        /* Create and fill out the kernel structure */
        hwrt = kzalloc(sizeof(*hwrt), GFP_KERNEL);
@@ -466,35 +466,36 @@ pvr_hwrt_dataset_create(struct pvr_file *pvr_file,
        if (!hwrt)
                return ERR_PTR(-ENOMEM);
 
-       kref_init(&hwrt->ref_count);
-
        err = hwrt_init_kernel_structure(pvr_file, args, hwrt);
        if (err < 0)
                goto err_free;
 
        err = hwrt_init_common_fw_structure(pvr_file, args, hwrt);
        if (err < 0)
-               goto err_free;
+               goto err_fini_kernel_structure;
 
-       for (int i = 0; i < ARRAY_SIZE(hwrt->data); i++) {
+       for (; i < ARRAY_SIZE(hwrt->data); i++) {
                err = hwrt_data_init_fw_structure(pvr_file, hwrt, args,
                                                  &args->rt_data_args[i],
                                                  &hwrt->data[i]);
-               if (err < 0) {
-                       i--;
-                       /* Destroy already created structures. */
-                       for (; i >= 0; i--)
-                               hwrt_data_fini_fw_structure(hwrt, i);
-                       goto err_free;
-               }
+               if (err < 0)
+                       goto err_fini_data_structures;
 
                hwrt->data[i].hwrt_dataset = hwrt;
        }
 
+       kref_init(&hwrt->ref_count);
        return hwrt;
 
+err_fini_data_structures:
+       while (--i >= 0)
+               hwrt_data_fini_fw_structure(hwrt, i);
+
+err_fini_kernel_structure:
+       hwrt_fini_kernel_structure(hwrt);
+
 err_free:
-       pvr_hwrt_dataset_put(hwrt);
+       kfree(hwrt);
 
        return ERR_PTR(err);
 }
-- 
2.25.1