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Subject[tip:core/urgent] linux/kernel.h: Use parentheses around argument in u64_to_user_ptr()
Commit-ID:  a0fe2c6479aab5723239b315ef1b552673f434a3
Gitweb: https://git.kernel.org/tip/a0fe2c6479aab5723239b315ef1b552673f434a3
Author: Jann Horn <jannh@google.com>
AuthorDate: Fri, 29 Mar 2019 22:46:49 +0100
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Wed, 3 Apr 2019 11:43:49 +0200

linux/kernel.h: Use parentheses around argument in u64_to_user_ptr()

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
---
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 34a5036debd3..2d14e21c16c0 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -47,8 +47,8 @@

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

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