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    Subject[PATCH 4.15 085/105] x86/vsyscall/64: Use proper accessor to update P4D entry
    Date
    4.15-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

    commit 31ad7f8e7dc94d3b85ccf9b6141ce6dfd35a1781 upstream.

    Writing to it directly does not work for Xen PV guests.

    Fixes: 49275fef986a ("x86/vsyscall/64: Explicitly set _PAGE_USER in the pagetable hierarchy")
    Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Juergen Gross <jgross@suse.com>
    Acked-by: Andy Lutomirski <luto@kernel.org>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/20180319143154.3742-1-boris.ostrovsky@oracle.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/x86/entry/vsyscall/vsyscall_64.c
    +++ b/arch/x86/entry/vsyscall/vsyscall_64.c
    @@ -355,7 +355,7 @@ void __init set_vsyscall_pgtable_user_bi
    set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
    p4d = p4d_offset(pgd, VSYSCALL_ADDR);
    #if CONFIG_PGTABLE_LEVELS >= 5
    - p4d->p4d |= _PAGE_USER;
    + set_p4d(p4d, __p4d(p4d_val(*p4d) | _PAGE_USER));
    #endif
    pud = pud_offset(p4d, VSYSCALL_ADDR);
    set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));

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