linux-kernel - [PATCH 3.12 031/111] ARM: 8051/1: put_user: fix possible data corruption in put

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Message-Id: <add232a1a6031431736e0c774cb8e1e7fe89db60.1403512281.git.jslaby@suse.cz>
Date:	Mon, 23 Jun 2014 10:31:06 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 031/111] ARM: 8051/1: put_user: fix possible data corruption in put_user

From: Andrey Ryabinin <a.ryabinin@...sung.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 537094b64b229bf3ad146042f83e74cf6abe59df upstream.

According to arm procedure call standart r2 register is call-cloberred.
So after the result of x expression was put into r2 any following
function call in p may overwrite r2. To fix this, the result of p
expression must be saved to the temporary variable before the
assigment x expression to __r2.

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
Reviewed-by: Nicolas Pitre <nico@...aro.org>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/arm/include/asm/uaccess.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 72abdc541f38..7f3f3cc25d7e 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -171,8 +171,9 @@ extern int __put_user_8(void *, unsigned long long);
 #define __put_user_check(x,p)							\
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
+		const typeof(*(p)) __user *__tmp_p = (p);		\
 		register const typeof(*(p)) __r2 asm("r2") = (x);	\
-		register const typeof(*(p)) __user *__p asm("r0") = (p);\
+		register const typeof(*(p)) __user *__p asm("r0") = __tmp_p; \
 		register unsigned long __l asm("r1") = __limit;		\
 		register int __e asm("r0");				\
 		switch (sizeof(*(__p))) {				\
-- 
2.0.0

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