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    Subject[PATCH 4.18 09/79] x86/speculation/l1tf: Make sure the first page is always reserved
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: Andi Kleen <ak@linux.intel.com>

    The L1TF workaround doesn't make any attempt to mitigate speculate accesses
    to the first physical page for zeroed PTEs. Normally it only contains some
    data from the early real mode BIOS.

    It's not entirely clear that the first page is reserved in all
    configurations, so add an extra reservation call to make sure it is really
    reserved. In most configurations (e.g. with the standard reservations)
    it's likely a nop.

    Signed-off-by: Andi Kleen <ak@linux.intel.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Acked-by: Dave Hansen <dave.hansen@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kernel/setup.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/arch/x86/kernel/setup.c
    +++ b/arch/x86/kernel/setup.c
    @@ -823,6 +823,12 @@ void __init setup_arch(char **cmdline_p)
    memblock_reserve(__pa_symbol(_text),
    (unsigned long)__bss_stop - (unsigned long)_text);

    + /*
    + * Make sure page 0 is always reserved because on systems with
    + * L1TF its contents can be leaked to user processes.
    + */
    + memblock_reserve(0, PAGE_SIZE);
    +
    early_reserve_initrd();

    /*

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