linux-kernel - Re: [PATCH] mm/vmalloc: Don't allow VM_NO

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Message-ID: <202109160857.8F4AAE1A19@keescook>
Date:   Thu, 16 Sep 2021 08:57:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, Will Deacon <will@...nel.org>,
        andreyknvl@...il.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH] mm/vmalloc: Don't allow VM_NO_GUARD on vmap()

On Thu, Sep 16, 2021 at 12:41:56PM +0200, Peter Zijlstra wrote:
> 
> The vmalloc guard pages are added on top of each allocation, thereby
> isolating any two allocations from one another. The top guard of the
> lower allocation is the bottom guard guard of the higher allocation
> etc.
> 
> Therefore VM_NO_GUARD is dangerous; it breaks the basic premise of
> isolating separate allocations.
> 
> There are only two in-tree users of this flag, neither of which use it
> through the exported interface. Ensure it stays this way.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Yes, please. :)

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook