linux-kernel - Re: [PATCH] x86/mm: Fix leak of pmd ptlock

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Message-ID: <df5209ad-e527-92ce-52a2-33e1aa9deaff@intel.com>
Date:   Tue, 5 Jan 2021 07:40:16 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Dan Williams <dan.j.williams@...el.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de
Cc:     stable@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Yi Zhang <yi.zhang@...hat.com>,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        willy@...radead.org
Subject: Re: [PATCH] x86/mm: Fix leak of pmd ptlock

On 12/2/20 10:28 PM, Dan Williams wrote:
> Commit 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
> introduced a new location where a pmd was released, but neglected to run
> the pmd page destructor. In fact, this happened previously for a
> different pmd release path and was fixed by commit:
> 
> c283610e44ec ("x86, mm: do not leak page->ptl for pmd page tables").
> 
> This issue was hidden until recently because the failure mode is silent,
> but commit:

Looks sane.  Thanks as always for the thorough changelog and the
investigation into why we're suddenly seeing this now.

I agree that ridding ourselves of open-coded free_page()'s is a good
idea, but this patch itself needs to be around for stable anyway.  So,

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>