[bug report] drm/gpusvm: Add support for GPU Shared Virtual Memory

[Dan Carpenter]

Hello Matthew Brost,

Commit 99624bdff867 ("drm/gpusvm: Add support for GPU Shared Virtual
Memory") from Mar 5, 2025 (linux-next), leads to the following Smatch
static checker warning:

	drivers/gpu/drm/drm_gpusvm.c:794 drm_gpusvm_range_alloc()
	error: 'range' dereferencing possible ERR_PTR()

drivers/gpu/drm/drm_gpusvm.c
    777 static struct drm_gpusvm_range *
    778 drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,
    779                        struct drm_gpusvm_notifier *notifier,
    780                        unsigned long fault_addr, unsigned long chunk_size,
    781                        bool migrate_devmem)
    782 {
    783         struct drm_gpusvm_range *range;
    784 
    785         if (gpusvm->ops->range_alloc)
    786                 range = gpusvm->ops->range_alloc(gpusvm);

xe_svm_range_alloc() returns ERR_PTR(-ENOMEM).

    787         else
    788                 range = kzalloc(sizeof(*range), GFP_KERNEL);
    789 
    790         if (!range)
    791                 return ERR_PTR(-ENOMEM);
    792 
    793         kref_init(&range->refcount);
--> 794         range->gpusvm = gpusvm;
                ^^^^^^^^^^^^^

    795         range->notifier = notifier;
    796         range->itree.start = ALIGN_DOWN(fault_addr, chunk_size);
    797         range->itree.last = ALIGN(fault_addr + 1, chunk_size) - 1;
    798         INIT_LIST_HEAD(&range->entry);
    799         range->notifier_seq = LONG_MAX;
    800         range->flags.migrate_devmem = migrate_devmem ? 1 : 0;
    801 
    802         return range;
    803 }

regards,
dan carpenter