accel/amdxdna: Prevent ubuf size overflow

The ubuf size calculation may overflow, resulting in an undersized
allocation and possible memory corruption.

Use check_add_overflow() helpers to validate the size calculation before
allocation.

Fixes: bd72d4a ("accel/amdxdna: Support user space allocated buffer")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260217192815.1784689-1-lizhi.hou@amd.com

Author: houlz0507

drivers/accel/amdxdna/amdxdna_ubuf.c

@@ -7,6 +7,7 @@
 #include <drm/drm_device.h>
 #include <drm/drm_print.h>
 #include <linux/dma-buf.h>
+#include <linux/overflow.h>
 #include <linux/pagemap.h>
 #include <linux/vmalloc.h>
 
@@ -176,7 +177,10 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,
 			goto free_ent;
 		}
 
-		exp_info.size += va_ent[i].len;
+		if (check_add_overflow(exp_info.size, va_ent[i].len, &exp_info.size)) {
+			ret = -EINVAL;
+			goto free_ent;
+		}
 	}
 
 	ubuf->nr_pages = exp_info.size >> PAGE_SHIFT;