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Re: [PATCH for-4.16] x86/shstk: Fix use of shadow stacks with XPTI active
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 2 Nov 2021 16:14:19 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 02 Nov 2021 15:14:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.11.2021 15:39, Andrew Cooper wrote:
> The call to setup_cpu_root_pgt(0) in smp_prepare_cpus() is too early. It
> clones the BSP's stack while the .data mapping is still in use, causing all
> mappings to be fully read read/write (and with no guard pages either). This
> ultimately causes #DF when trying to enter the dom0 kernel for the first time.
>
> Defer setting up BSPs XPTI pagetable until reinit_bsp_stack() after we've set
> up proper shadow stack permissions.
>
> Fixes: 60016604739b ("x86/shstk: Rework the stack layout to support shadow
> stacks")
> Fixes: b60ab42db2f0 ("x86/shstk: Activate Supervisor Shadow Stacks")
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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