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SubjectRe: [PATCH 3/3] riscv: fix __user annotation for __copy_user()
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On 6/1/18 8:22 AM, Luc Van Oostenryck wrote:
> __copy_user() is a function, written in assembly, used to copy
> memory between kernel & user space. As such its to & from args
> may both take a user pointer or a kernel pointer.
>
> However the prototype for this function declare these two args
> as 'void __user *', which is no more & no less correct than
> declaring them as 'void *'. In fact theer is no possible correct

/s/theer/there

> annotation for such a function.
>
> The problem is worked around here by declaring these args as
> unsigned long and casting them to the right type in each of
> two callers raw_copy_{to,from}_user() as some kind of cast would
> be needed anyway.
>
> Note: another solution, maybe cleaner but slightly more complex,
> would be to declare two version of __copy_user,
> either in the asm file or via an alias, each having already
> the correct typing for raw_copy_{to,from}_user().
>

I feel that would be a better solution as it is implemented similarly
in ARM as well.

I am unable to understand how "unsigned long" is better than "void*".
x86 implementation has both arguments as void*. Can you please clarify ?


Regards,
Atish
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> ---
> arch/riscv/include/asm/uaccess.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index 14b0b22fb..c7a6a4a4a 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -392,19 +392,19 @@ do { \
> })
>
>
> -extern unsigned long __must_check __copy_user(void __user *to,
> - const void __user *from, unsigned long n);
> +extern unsigned long __must_check __copy_user(unsigned long to,
> + const unsigned long from, unsigned long n);
>
> static inline unsigned long
> raw_copy_from_user(void *to, const void __user *from, unsigned long n)
> {
> - return __copy_user(to, from, n);
> + return __copy_user((unsigned long)to, (unsigned long)from, n);
> }
>
> static inline unsigned long
> raw_copy_to_user(void __user *to, const void *from, unsigned long n)
> {
> - return __copy_user(to, from, n);
> + return __copy_user((unsigned long)to, (unsigned long)from, n);
> }
>
> extern long strncpy_from_user(char *dest, const char __user *src, long count);
>

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