From: Matthew Wilcox <willy@infradead.org>
To: Jann Horn <jannh@google.com>
Cc: Jan Kara <jack@suse.cz>, Linux-MM <linux-mm@kvack.org>
Subject: Re: get_user_pages pinning: 2^22 page refs max?
Date: Wed, 1 May 2019 18:44:22 -0700 [thread overview]
Message-ID: <20190502014422.GA8099@bombadil.infradead.org> (raw)
In-Reply-To: <CAG48ez3C11j5On4kqwSBCZGtpS5XMohwEyT_2ei=aoaTex7D9Q@mail.gmail.com>
On Wed, May 01, 2019 at 06:19:00PM -0400, Jann Horn wrote:
> Regarding the LSFMM talk today:
> So with the page ref bias, the maximum number of page references will
> be something like 2^22, right? Is the bias only applied to writable
> references or also readonly ones?
2^21, because it's going to get caught by the < 0 check.
I think that's fine, though. Anyone trying to map that page so many times
is clearly doing something either malicious or inadvertently very wrong.
After the 2 millionth time, attempting to pin the page will fail, and
the application will have to deal with that failure.
next prev parent reply other threads:[~2019-05-02 1:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-01 22:19 get_user_pages pinning: 2^22 page refs max? Jann Horn
2019-05-02 1:44 ` Matthew Wilcox [this message]
2019-05-02 15:24 ` Jan Kara
2019-05-02 15:34 ` Matthew Wilcox
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