linux-kernel - [tip:x86/asm] x86/uaccess: Fix implicit cast of _

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Date:   Wed, 3 Apr 2019 08:10:11 -0700
From:   tip-bot for Jann Horn <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     qiaowei.ren@...el.com, will.deacon@....com, hpa@...or.com,
        luto@...nel.org, mingo@...hat.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, bp@...e.de,
        akpm@...ux-foundation.org, mingo@...nel.org, mojha@...eaurora.org,
        x86@...nel.org, jannh@...gle.com, rppt@...ux.ibm.com
Subject: [tip:x86/asm] x86/uaccess: Fix implicit cast of __user pointer

Commit-ID:  a6cbfbe6677efb5ca47bb7958c2718236c25126e
Gitweb:     https://git.kernel.org/tip/a6cbfbe6677efb5ca47bb7958c2718236c25126e
Author:     Jann Horn <jannh@...gle.com>
AuthorDate: Fri, 29 Mar 2019 22:46:52 +0100
Committer:  Borislav Petkov <bp@...e.de>
CommitDate: Wed, 3 Apr 2019 16:26:17 +0200

x86/uaccess: Fix implicit cast of __user pointer

The first two arguments of __user_atomic_cmpxchg_inatomic() are:

 - @uval is a kernel pointer into which the old value should be stored
 - @ptr is the user pointer on which the cmpxchg should operate

This means that casting @uval to __typeof__(ptr) is wrong. Since @uval
is only used once inside the macro, just get rid of __uval and use
(uval) directly.

Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Mukesh Ojha <mojha@...eaurora.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Qiaowei Ren <qiaowei.ren@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will.deacon@....com>
Cc: x86-ml <x86@...nel.org>
Link: https://lkml.kernel.org/r/20190329214652.258477-4-jannh@google.com
---
 arch/x86/include/asm/uaccess.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1954dd5552a2..a21f2a2f17bf 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -585,7 +585,6 @@ extern void __cmpxchg_wrong_size(void)
 #define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size)	\
 ({									\
 	int __ret = 0;							\
-	__typeof__(ptr) __uval = (uval);				\
 	__typeof__(*(ptr)) __old = (old);				\
 	__typeof__(*(ptr)) __new = (new);				\
 	__uaccess_begin_nospec();					\
@@ -661,7 +660,7 @@ extern void __cmpxchg_wrong_size(void)
 		__cmpxchg_wrong_size();					\
 	}								\
 	__uaccess_end();						\
-	*__uval = __old;						\
+	*(uval) = __old;						\
 	__ret;								\
 })