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    Subject[PATCH 4.4 28/72] arm64: avoid overflow in VA_START and PAGE_OFFSET
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Nick Desaulniers <ndesaulniers@google.com>

    commit 82cd588052815eb4146f9f7c5347ca5e32c56360 upstream.

    The bitmask used to define these values produces overflow, as seen by
    this compiler warning:

    arch/arm64/kernel/head.S:47:8: warning:
    integer overflow in preprocessor expression
    #elif (PAGE_OFFSET & 0x1fffff) != 0
    ^~~~~~~~~~~
    arch/arm64/include/asm/memory.h:52:46: note:
    expanded from macro 'PAGE_OFFSET'
    #define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS -
    1))
    ~~~~~~~~~~~~~~~~~~ ^

    It would be preferrable to use GENMASK_ULL() instead, but it's not set
    up to be used from assembly (the UL() macro token pastes UL suffixes
    when not included in assembly sources).

    Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Suggested-by: Yury Norov <ynorov@caviumnetworks.com>
    Suggested-by: Matthias Kaehlcke <mka@chromium.org>
    Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    [natechancellor: KIMAGE_VADDR doesn't exist]
    Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm64/include/asm/memory.h | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/arch/arm64/include/asm/memory.h
    +++ b/arch/arm64/include/asm/memory.h
    @@ -49,8 +49,10 @@
    * and PAGE_OFFSET - it must be within 128MB of the kernel text.
    */
    #define VA_BITS (CONFIG_ARM64_VA_BITS)
    -#define VA_START (UL(0xffffffffffffffff) << VA_BITS)
    -#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
    +#define VA_START (UL(0xffffffffffffffff) - \
    + (UL(1) << VA_BITS) + 1)
    +#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
    + (UL(1) << (VA_BITS - 1)) + 1)
    #define MODULES_END (PAGE_OFFSET)
    #define MODULES_VADDR (MODULES_END - SZ_64M)
    #define PCI_IO_END (MODULES_VADDR - SZ_2M)

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