linux-kernel - [PATCH 03/10] floppy: Fix MAX

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Date:   Wed, 15 Mar 2023 14:31:26 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Denis Efremov <efremov@...ux.com>
Subject: [PATCH 03/10] 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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Denis Efremov <efremov@...ux.com>
---
 drivers/block/floppy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 487840e3564d..90d2dfb6448e 100644
--- a/drivers/block/floppy.c
+++ b/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);
-- 
2.39.2