floppy: fix MAX_ORDER usage

MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
can deliver is MAX_ORDER-1.

Fix MAX_ORDER usage in floppy code.

Also allocation buffer exactly PAGE_SIZE << MAX_ORDER bytes is okay. Fix
MAX_LEN check.

Link: https://lkml.kernel.org/r/20230315113133.11326-4-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Denis Efremov <efremov@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/floppy.c

@@ -3079,7 +3079,7 @@ static void raw_cmd_free(struct floppy_raw_cmd **ptr)
 	}
 }
 
-#define MAX_LEN (1UL << MAX_ORDER << PAGE_SHIFT)
+#define MAX_LEN (1UL << (MAX_ORDER - 1) << PAGE_SHIFT)
 
 static int raw_cmd_copyin(int cmd, void __user *param,
 				 struct floppy_raw_cmd **rcmd)
@@ -3108,7 +3108,7 @@ static int raw_cmd_copyin(int cmd, void __user *param,
 	ptr->resultcode = 0;
 
 	if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
-		if (ptr->length <= 0 || ptr->length >= MAX_LEN)
+		if (ptr->length <= 0 || ptr->length > MAX_LEN)
 			return -EINVAL;
 		ptr->kernel_data = (char *)fd_dma_mem_alloc(ptr->length);
 		fallback_on_nodma_alloc(&ptr->kernel_data, ptr->length);