linux-kernel - Re: [PATCH 2/2] riscv: Fix sparse warning about different address spaces

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Message-ID: <2fb511b8-4841-40e1-a364-e52dad51e300@tenstorrent.com>
Date: Thu, 4 Sep 2025 10:42:49 +1000
From: Cyril Bur <cyrilbur@...storrent.com>
To: Alexandre Ghiti <alexghiti@...osinc.com>,
 kernel test robot <lkp@...el.com>, Al Viro <viro@...iv.linux.org.uk>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Jisheng Zhang <jszhang@...nel.org>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH 2/2] riscv: Fix sparse warning about different address
 spaces



On 4/9/2025 4:53 am, Alexandre Ghiti wrote:
> We did not propagate the __user attribute of the pointers in
> __get_kernel_nofault() and __put_kernel_nofault(), which results in
> sparse complaining:
> 
>>> mm/maccess.c:41:17: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const [noderef] __user *from @@     got unsigned long long [usertype] * @@
>     mm/maccess.c:41:17: sparse:     expected void const [noderef] __user *from
>     mm/maccess.c:41:17: sparse:     got unsigned long long [usertype] *
> 
> So fix this by correctly casting those pointers.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202508161713.RWu30Lv1-lkp@intel.com/
> Suggested-by: Al Viro <viro@...iv.linux.org.uk>
> Fixes: f6bff7827a48 ("riscv: uaccess: use 'asm_goto_output' for get_user()")
> Cc: stable@...r.kernel.org
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>

Reviewed-by: Cyril Bur <cyrilbur@...storrent.com>

> ---
>   arch/riscv/include/asm/uaccess.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index 551e7490737effb2c238e6a4db50293ece7c9df9..f5f4f7f85543f2a635b18e4bd1c6202b20e3b239 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -438,10 +438,10 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
>   }
>   
>   #define __get_kernel_nofault(dst, src, type, err_label)			\
> -	__get_user_nocheck(*((type *)(dst)), (type *)(src), err_label)
> +	__get_user_nocheck(*((type *)(dst)), (__force __user type *)(src), err_label)
>   
>   #define __put_kernel_nofault(dst, src, type, err_label)			\
> -	__put_user_nocheck(*((type *)(src)), (type *)(dst), err_label)
> +	__put_user_nocheck(*((type *)(src)), (__force __user type *)(dst), err_label)
>   
>   static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
>   {
>