udmabuf: fix a buf size overflow issue during udmabuf creation

by casting size_limit_mb to u64  when calculate pglimit.

Signed-off-by: Xiaogang Chen<Xiaogang.Chen@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250321164126.329638-1-xiaogang.chen@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/dma-buf/udmabuf.c

@@ -393,7 +393,7 @@ static long udmabuf_create(struct miscdevice *device,
 	if (!ubuf)
 		return -ENOMEM;
 
-	pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
+	pglimit = ((u64)size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
 	for (i = 0; i < head->count; i++) {
 		pgoff_t subpgcnt;