linux-kernel - Re: [PATCH STABLE 4.9] x86, mm, gup: prevent get_page() race with munmap in paravirt guest

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Message-ID: <78bbba27-81ed-40db-eb6e-5add997b2027@suse.cz>
Date:   Mon, 23 Sep 2019 10:48:04 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Ben Hutchings <ben@...adent.org.uk>, stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        Jann Horn <jannh@...gle.com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        xen-devel@...ts.xenproject.org, Oscar Salvador <osalvador@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juergen Gross <jgross@...e.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH STABLE 4.9] x86, mm, gup: prevent get_page() race with
 munmap in paravirt guest

On 9/19/19 8:26 PM, Ben Hutchings wrote:
> On Mon, 2019-08-19 at 18:58 +0100, Vlastimil Babka wrote:
> [...]
>> Hi, I'm sending this stable-only patch for consideration because it's probably
>> unrealistic to backport the 4.13 switch to generic GUP. I can look at 4.4 and
>> 3.16 if accepted. The RCU page table freeing could be also considered.
> 
> I would be interested in backports for 3.16 and 4.4.
> 
>> Note the patch also includes page refcount protection. I found out that
>> 8fde12ca79af ("mm: prevent get_user_pages() from overflowing page refcount")
>> backport to 4.9 missed the arch-specific gup implementations:
>> https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@suse.cz/
> [...]
> 
> I suppose that still needs to be addressed for 4.9, right?

Yeah, I'll take a look, thanks for reminding.

> Ben.
>