drm/buddy: Fix alloc_range() error handling code

Few users have observed display corruption when they boot
the machine to KDE Plasma or playing games. We have root
caused the problem that whenever alloc_range() couldn't
find the required memory blocks the function was returning
SUCCESS in some of the corner cases.

The right approach would be if the total allocated size
is less than the required size, the function should
return -ENOSPC.

Cc: <stable@vger.kernel.org> # 6.7+
Fixes: 0a1844b ("drm/buddy: Improve contiguous memory allocation")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3097
Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240207174456.341121-1-Arunpravin.PaneerSelvam@amd.com/
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240214131853.5934-1-Arunpravin.PaneerSelvam@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/drm_buddy.c

@@ -539,6 +539,12 @@ static int __alloc_range(struct drm_buddy *mm,
 	} while (1);
 
 	list_splice_tail(&allocated, blocks);
+
+	if (total_allocated < size) {
+		err = -ENOSPC;
+		goto err_free;
+	}
+
 	return 0;
 
 err_undo: