linux-kernel - Re: [PATCH] x86/mm: Handle physical-virtual alignment mismatch in phys_p4d

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Message-ID: <4ecd0603-e847-1cae-bafa-e892d79b7259@intel.com>
Date:   Thu, 20 Jun 2019 07:42:55 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kyle Pelton <kyle.d.pelton@...el.com>,
        Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH] x86/mm: Handle physical-virtual alignment mismatch in
 phys_p4d_init()

On 6/20/19 4:22 AM, Kirill A. Shutemov wrote:
> The commit relaxes KASLR alignment requirements and it can lead to
> mismatch bentween 'i' and 'p4d_index(vaddr)' inside the loop in
> phys_p4d_init(). The mismatch in its turn leads to clearing wrong p4d
> entry and eventually to the oops.

Just curious, but what does it relax the requirement to and from?

I'm just not clearly spotting the actual bug.