linux-kernel - [PATCH 4.19 31/66] linux/kernel.h: Use parentheses around argument in u64_to_user

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Date:   Thu,  9 May 2019 20:42:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jann Horn <jannh@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Andrei Vagin <avagin@...nvz.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Jani Nikula <jani.nikula@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        NeilBrown <neilb@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Qiaowei Ren <qiaowei.ren@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86-ml <x86@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 31/66] linux/kernel.h: Use parentheses around argument in u64_to_user_ptr()

[ 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@...gle.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Mukesh Ojha <mojha@...eaurora.org>
Cc: Andrei Vagin <avagin@...nvz.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jani Nikula <jani.nikula@...el.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: NeilBrown <neilb@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Qiaowei Ren <qiaowei.ren@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86-ml <x86@...nel.org>
Link: https://lkml.kernel.org/r/20190329214652.258477-1-jannh@google.com
Signed-off-by: Sasha Levin <sashal@...nel.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 d6aac75b51baa..3d83ebb302cfd 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);	\
 }					\
 )
 
-- 
2.20.1