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    SubjectRe: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary
    On Wed, May 24, 2017 at 8:57 AM,  <riel@redhat.com> wrote:
    > From: Rik van Riel <riel@redhat.com>
    >
    > Use the ascii-armor canary to prevent unterminated C string overflows
    > from being able to successfully overwrite the canary, even if they
    > somehow obtain the canary value.
    >
    > Inspired by execshield ascii-armor and Daniel Micay's linux-hardened tree.
    >
    > Signed-off-by: Rik van Riel <riel@redhat.com>

    Acked-by: Kees Cook <keescook@chromium.org>

    -Kees

    > ---
    > arch/arm64/include/asm/stackprotector.h | 1 +
    > 1 file changed, 1 insertion(+)
    >
    > diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
    > index fe5e287dc56b..b86a0865ddf1 100644
    > --- a/arch/arm64/include/asm/stackprotector.h
    > +++ b/arch/arm64/include/asm/stackprotector.h
    > @@ -30,6 +30,7 @@ static __always_inline void boot_init_stack_canary(void)
    > /* Try to get a semi random initial value. */
    > get_random_bytes(&canary, sizeof(canary));
    > canary ^= LINUX_VERSION_CODE;
    > + canary &= CANARY_MASK;
    >
    > current->stack_canary = canary;
    > __stack_chk_guard = current->stack_canary;
    > --
    > 2.9.3
    >



    --
    Kees Cook
    Pixel Security

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