linux-kernel - [PATCH 3.4 06/88] ARM: 8051/1: put_user: fix possible data corruption in put

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Message-Id: <20140610002424.759690807@linuxfoundation.org>
Date:	Mon,  9 Jun 2014 17:24:16 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Andrey Ryabinin <a.ryabinin@...sung.com>,
	Nicolas Pitre <nico@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: [PATCH 3.4 06/88] ARM: 8051/1: put_user: fix possible data corruption in put_user

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

------------------

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

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/include/asm/uaccess.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -158,8 +158,9 @@ extern int __put_user_8(void *, unsigned
 #define put_user(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))) {				\


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