Re: [PATCH v1 01/15] powerpc/uaccess: Remove __get_user_allowed() and unsafe_op_wrap()

Daniel Axtens
2021-03-02T07:11:32Z

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> Those two macros have only one user which is unsafe_get_user().
>
> Put everything in one place and remove them.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/include/asm/uaccess.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 78e2a3990eab..8cbf3e3874f1 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -53,9 +53,6 @@ static inline bool __access_ok(unsigned long addr, unsigned long size)
> #define __put_user(x, ptr) \
> __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
>
> -#define __get_user_allowed(x, ptr) \
> - __get_user_nocheck((x), (ptr), sizeof(*(ptr)), false)
> -
> #define __get_user_inatomic(x, ptr) \
> __get_user_nosleep((x), (ptr), sizeof(*(ptr)))
> #define __put_user_inatomic(x, ptr) \
> @@ -482,8 +479,11 @@ user_write_access_begin(const void __user *ptr, size_t len)
> #define user_write_access_begin user_write_access_begin
> #define user_write_access_end prevent_current_write_to_user
>
> -#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
> -#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
> +#define unsafe_get_user(x, p, e) do { \
> + if (unlikely(__get_user_nocheck((x), (p), sizeof(*(p)), false)))\
> + goto e; \
> +} while (0)
> +

This seems correct to me.

Checkpatch does have one check that is relevant:

CHECK: Macro argument reuse 'p' - possible side-effects?
#36: FILE: arch/powerpc/include/asm/uaccess.h:482:
+#define unsafe_get_user(x, p, e) do { \
+ if (unlikely(__get_user_nocheck((x), (p), sizeof(*(p)), false)))\
+ goto e; \
+} while (0)

Given that we are already creating a new block, should we do something
like this (completely untested):

#define unsafe_get_user(x, p, e) do { \
__typeof__(p) __p = (p);
if (unlikely(__get_user_nocheck((x), (__p), sizeof(*(__p)), false)))\
goto e; \
} while (0)

Kind regards,
Daniel

> #define unsafe_put_user(x, p, e) \
> __unsafe_put_user_goto((__typeof__(*(p)))(x), (p), sizeof(*(p)), e)
>
> --
> 2.25.0