On Tue, 6 May 2014, Andrey Ryabinin wrote:
> 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@xxxxxxxxxxx>
> Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Please push this patch into Russell's patch system.
Thanks.
> ---
> Since v1:
> - tmp_p variable renamed to __tmp_p
> - added Reviewed-by tag
> - added Cc: stable@xxxxxxxxxxxxxxx
>
> 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 12c3a5d..75d9579 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))) { \
> --
> 1.8.5.5
>
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