linux-kernel - Re: [PATCH v2] mm/memory.c: do_fault: avoid usage of stale vm_area

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Message-ID: <20190302185144.GD31083@redhat.com>
Date:   Sat, 2 Mar 2019 13:51:44 -0500
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Jan Stancek <jstancek@...hat.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, willy@...radead.org,
        peterz@...radead.org, riel@...riel.com, mhocko@...e.com,
        ying.huang@...el.com, jrdr.linux@...il.com, jglisse@...hat.com,
        aneesh.kumar@...ux.ibm.com, david@...hat.com, raquini@...hat.com,
        rientjes@...gle.com, kirill@...temov.name,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/memory.c: do_fault: avoid usage of stale
 vm_area_struct

Hello Jan,

On Sat, Mar 02, 2019 at 07:19:39PM +0100, Jan Stancek wrote:
> +	struct mm_struct *vm_mm = READ_ONCE(vma->vm_mm);

The vma->vm_mm cannot change under gcc there, so no need of
READ_ONCE. The release of mmap_sem has release semantics so the
vma->vm_mm access cannot be reordered after up_read(mmap_sem) either.

Other than the above detail:

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>

Thanks,
Andrea