linux-kernel - Re: [PATCH 4.19 84/86] efi/x86: Handle by-ref arguments covering multiple pages in mixed mode

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Message-ID: <20200312035235.GA270934@rani.riverdale.lan>
Date:   Wed, 11 Mar 2020 23:52:37 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, linux-efi@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 4.19 84/86] efi/x86: Handle by-ref arguments covering
 multiple pages in mixed mode

On Wed, Mar 11, 2020 at 02:01:07PM +0100, Pavel Machek wrote:
> We don't really need to do this computation on pa, it would work on va
> as well, right? It does not matter much, but old code worked that way.
> 
> Plus, strictly speaking, pa + size can overflow for huge sizes, and
> test will return false negatives.

This is 64-bit code, overflow would need pa + size to be bigger than
2^64, and even then a false negative would need size to be around 2^64.