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

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@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>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index cd8b589111ba71bab9b52192521cf87042dfec11..35c9db857ebe9c7d53715ec42518a6e9fbe1dc6e 100644 (file)
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -251,7 +251,7 @@ extern int __put_user_8(void *, unsigned long long);
        ({                                                              \
                unsigned long __limit = current_thread_info()->addr_limit - 1; \
                const typeof(*(p)) __user *__tmp_p = (p);               \
-               register typeof(*(p)) __r2 asm("r2") = (x);     \
+               register const typeof(*(p)) __r2 asm("r2") = (x);       \
                register const typeof(*(p)) __user *__p asm("r0") = __tmp_p; \
                register unsigned long __l asm("r1") = __limit;         \
                register int __e asm("r0");                             \