ARM: 8051/1: put_user: fix possible data corruption in put_user

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@samsung.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 12c3a5decc60..75d95799b6e6 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))) {                               \