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SubjectRe: [PATCH v2 4/4] x86/uaccess: Fix implicit cast of __user pointer
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On 3/29/2019 10:00 PM, Jann Horn wrote:
> The first two arguments of __user_atomic_cmpxchg_inatomic() are:
>
> - `uval` is a kernel pointer into which the old value should be stored
> - `ptr` is the user pointer on which the cmpxchg should operate
>
> This means that casting `uval` to `__typeof__(ptr)` is wrong. Since `uval`
> is only used once inside the macro, just get rid of __uval and use `(uval)`
> directly.
>
> Signed-off-by: Jann Horn <jannh@google.com>

Looks good to me.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

Cheers,
-Mukesh

> ---
> arch/x86/include/asm/uaccess.h | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 1954dd5552a2..a21f2a2f17bf 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -585,7 +585,6 @@ extern void __cmpxchg_wrong_size(void)
> #define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size) \
> ({ \
> int __ret = 0; \
> - __typeof__(ptr) __uval = (uval); \
> __typeof__(*(ptr)) __old = (old); \
> __typeof__(*(ptr)) __new = (new); \
> __uaccess_begin_nospec(); \
> @@ -661,7 +660,7 @@ extern void __cmpxchg_wrong_size(void)
> __cmpxchg_wrong_size(); \
> } \
> __uaccess_end(); \
> - *__uval = __old; \
> + *(uval) = __old; \
> __ret; \
> })
>

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