linux-kernel - Re: [PATCH 07/14] uaccess: generalize access

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Message-ID: <YgqOLZbFK7/B2HJT@zeniv-ca.linux.org.uk>
Date:   Mon, 14 Feb 2022 17:15:25 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-api@...r.kernel.org, arnd@...db.de,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        will@...nel.org, guoren@...nel.org, bcain@...eaurora.org,
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Subject: Re: [PATCH 07/14] uaccess: generalize access_ok()

On Mon, Feb 14, 2022 at 05:34:45PM +0100, Arnd Bergmann wrote:

> diff --git a/arch/csky/kernel/signal.c b/arch/csky/kernel/signal.c
> index c7b763d2f526..8867ddf3e6c7 100644
> --- a/arch/csky/kernel/signal.c
> +++ b/arch/csky/kernel/signal.c
> @@ -136,7 +136,7 @@ static inline void __user *get_sigframe(struct ksignal *ksig,
>  static int
>  setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
>  {
> -	struct rt_sigframe *frame;
> +	struct rt_sigframe __user *frame;
>  	int err = 0;
>  
>  	frame = get_sigframe(ksig, regs, sizeof(*frame));

Minor nit: might make sense to separate annotations (here, on nios2, etc.) from the rest...

This, OTOH,

> diff --git a/arch/sparc/include/asm/uaccess_64.h b/arch/sparc/include/asm/uaccess_64.h
> index 5c12fb46bc61..000bac67cf31 100644
> --- a/arch/sparc/include/asm/uaccess_64.h
> +++ b/arch/sparc/include/asm/uaccess_64.h
...
> -static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
> -{
> -	if (__builtin_constant_p(size))
> -		return addr > limit - size;
> -
> -	addr += size;
> -	if (addr < size)
> -		return true;
> -
> -	return addr > limit;
> -}
> -
> -#define __range_not_ok(addr, size, limit)                               \
> -({                                                                      \
> -	__chk_user_ptr(addr);                                           \
> -	__chk_range_not_ok((unsigned long __force)(addr), size, limit); \
> -})
> -
> -static inline int __access_ok(const void __user * addr, unsigned long size)
> -{
> -	return 1;
> -}
> -
> -static inline int access_ok(const void __user * addr, unsigned long size)
> -{
> -	return 1;
> -}
> +#define __range_not_ok(addr, size, limit) (!__access_ok(addr, size))

is really wrong.  For sparc64, access_ok() should always be true.
This __range_not_ok() thing is used *only* for valid_user_frame() in
arch/sparc/kernel/perf_event.c - it's not a part of normal access_ok()
there.

sparc64 has separate address spaces for kernel and for userland; access_ok()
had never been useful there.