linux-kernel - Re: [PATCH 1/1] Ddrivers: hv: Turn off write permission on the hypercall page

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Date:   Thu, 9 Feb 2017 17:12:01 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     kys@...hange.microsoft.com
Cc:     kys@...rosoft.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
        olaf@...fle.de, apw@...onical.com, vkuznets@...hat.com,
        jasowang@...hat.com, leann.ogasawara@...onical.com,
        keescook@...gle.com, sds@...ho.nsa.gov, <stable@...r.kernel.org>
Subject: Re: [PATCH 1/1] Ddrivers: hv: Turn off write permission on the
 hypercall page

On Wed,  8 Feb 2017 18:30:56 -0700
kys@...hange.microsoft.com wrote:

> From: K. Y. Srinivasan <kys@...rosoft.com>
> 
> The hypercall page only needs to be executable but currently it is setup to
> be writable as well. Fix the issue.
> 
> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> Cc: <stable@...r.kernel.org>
> ---
>  arch/x86/hyperv/hv_init.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index c224b7d..db64baf 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -125,7 +125,7 @@ void hyperv_init(void)
>  	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
>  	wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
>  
> -	hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_EXEC);
> +	hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
>  	if (hypercall_pg == NULL) {
>  		wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);

Verified that this fixes the original problem.
I don't see the warning anymore and the guest works normally.

Reported-by: Stephen Hemminger <stephen@...workplumber.org>
Tested-by: Stephen Hemminger <stephen@...workplumber.org>