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Date:   Sat, 10 Dec 2022 23:51:32 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Nhat Pham <nphamcs@gmail.com>
Cc:     akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, bfoster@redhat.com,
        willy@infradead.org, kernel-team@meta.com
Subject: Re: [PATCH v2 3/4] cachestat: implement cachestat syscall
Message-ID: <Y5UbhBTB2nSMN4UD@ZenIV>
References: <20221205175140.1543229-1-nphamcs@gmail.com>
 <20221205175140.1543229-4-nphamcs@gmail.com>
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On Mon, Dec 05, 2022 at 09:51:39AM -0800, Nhat Pham wrote:

> +	if (!access_ok(cstat, sizeof(struct cachestat)))
> +		return -EFAULT;

What for?  You are using copy_to_user() later, right?

> +	f = fdget(fd);
> +	if (f.file) {

It would be easier to read if you inverted the condition here.