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    Subject[PATCH 4.1 022/123] x86/init: Clear init_level4_pgt earlier
    Date
    4.1-stable review patch.  If anyone has any objections, please let me know.

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

    From: Andrey Ryabinin <a.ryabinin@samsung.com>

    commit d0f77d4d04b222a817925d33ba3589b190bfa863 upstream.

    Currently x86_64_start_kernel() has two KASAN related
    function calls. The first call maps shadow to early_level4_pgt,
    the second maps shadow to init_level4_pgt.

    If we move clear_page(init_level4_pgt) earlier, we could hide
    KASAN low level detail from generic x86_64 initialization code.
    The next patch will do it.

    Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
    Cc: Alexander Popov <alpopov@ptsecurity.com>
    Cc: Alexander Potapenko <glider@google.com>
    Cc: Andrey Konovalov <adech.fo@gmail.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dmitry Vyukov <dvyukov@google.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1435828178-10975-2-git-send-email-a.ryabinin@samsung.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/head64.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/arch/x86/kernel/head64.c
    +++ b/arch/x86/kernel/head64.c
    @@ -166,6 +166,8 @@ asmlinkage __visible void __init x86_64_
    /* clear bss before set_intr_gate with early_idt_handler */
    clear_bss();

    + clear_page(init_level4_pgt);
    +
    for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
    set_intr_gate(i, early_idt_handler_array[i]);
    load_idt((const struct desc_ptr *)&idt_descr);
    @@ -177,7 +179,6 @@ asmlinkage __visible void __init x86_64_
    */
    load_ucode_bsp();

    - clear_page(init_level4_pgt);
    /* set init_level4_pgt kernel high mapping*/
    init_level4_pgt[511] = early_level4_pgt[511];




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