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    Subject[PATCH AUTOSEL 4.19 26/53] linux/kernel.h: Use parentheses around argument in u64_to_user_ptr()
    Date
    From: Jann Horn <jannh@google.com>

    [ Upstream commit a0fe2c6479aab5723239b315ef1b552673f434a3 ]

    Use parentheses around uses of the argument in u64_to_user_ptr() to
    ensure that the cast doesn't apply to part of the argument.

    There are existing uses of the macro of the form

    u64_to_user_ptr(A + B)

    which expands to

    (void __user *)(uintptr_t)A + B

    (the cast applies to the first operand of the addition, the addition
    is a pointer addition). This happens to still work as intended, the
    semantic difference doesn't cause a difference in behavior.

    But I want to use u64_to_user_ptr() with a ternary operator in the
    argument, like so:

    u64_to_user_ptr(A ? B : C)

    This currently doesn't work as intended.

    Signed-off-by: Jann Horn <jannh@google.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
    Cc: Andrei Vagin <avagin@openvz.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Dan Carpenter <dan.carpenter@oracle.com>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Jani Nikula <jani.nikula@intel.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
    Cc: NeilBrown <neilb@suse.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Qiaowei Ren <qiaowei.ren@intel.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: x86-ml <x86@kernel.org>
    Link: https://lkml.kernel.org/r/20190329214652.258477-1-jannh@google.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/kernel.h | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/include/linux/kernel.h b/include/linux/kernel.h
    index d6aac75b51ba..3d83ebb302cf 100644
    --- a/include/linux/kernel.h
    +++ b/include/linux/kernel.h
    @@ -73,8 +73,8 @@

    #define u64_to_user_ptr(x) ( \
    { \
    - typecheck(u64, x); \
    - (void __user *)(uintptr_t)x; \
    + typecheck(u64, (x)); \
    + (void __user *)(uintptr_t)(x); \
    } \
    )

    --
    2.19.1
    \
     
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