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Date: Mon, 4 Dec 2017 21:24:07 -0800
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] dax: fix potential overflow on 32bit machine
Message-ID: <20171205052407.GA20757@bombadil.infradead.org>
References: <20171205033210.38338-1-yi.zhang@huawei.com>
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To: "zhangyi (F)" <yi.zhang@huawei.com>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, mawilcox@microsoft.com, ross.zwisler@linux.intel.com, viro@zeniv.linux.org.uk, miaoxie@huawei.com

On Tue, Dec 05, 2017 at 11:32:10AM +0800, zhangyi (F) wrote:
> On 32bit machine, when mmap2 a large enough file with pgoff more than
> ULONG_MAX >> PAGE_SHIFT, it will trigger offset overflow and lead to
> unmap the wrong page in dax_insert_mapping_entry(). This patch cast
> pgoff to 64bit to prevent the overflow.

You're quite correct, and you've solved this problem the same way as the
other half-dozen users in the kernel with the problem, so good job.

I think we can do better though.  How does this look?