linux-kernel - Re: fix a hyperv W^X violation and remove vmalloc

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Date:   Thu, 18 Jun 2020 11:28:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dexuan Cui <decui@...rosoft.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: fix a hyperv W^X violation and remove vmalloc_exec

On Thu, Jun 18, 2020 at 08:43:04AM +0200, Christoph Hellwig wrote:
> Hi all,
> 
> Dexuan reported a W^X violation due to the fact that the hyper hypercall
> page due switching it to be allocated using vmalloc_exec.  The problem
> is that PAGE_KERNEL_EXEC as used by vmalloc_exec actually sets writable
> permissions in the pte.  This series fixes the issue by switching to the
> low-level __vmalloc_node_range interface that allows specifing more
> detailed permissions instead.  It then also open codes the other two
> callers and removes the somewhat confusing vmalloc_exec interface.

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

> Peter noted that the hyper hypercall page allocation also has another
> long standing issue in that it shouldn't use the full vmalloc but just
> the module space.  This issue is so far theoretical as the allocation is
> done early in the boot process.  I plan to fix it with another bigger
> series for 5.9.

Thanks!