Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire

2022-02-18 Thread Arnd Bergmann 
On Fri, Feb 18, 2022 at 10:00 AM Geert Uytterhoeven
 wrote:
> >  /* We let the MMU do all checking */
> > -static inline int access_ok(const void __user *addr,
> > +static inline int access_ok(const void __user *ptr,
> > unsigned long size)
> >  {
> > +   unsigned long limit = TASK_SIZE;
> > +   unsigned long addr = (unsigned long)ptr;
> > +
> > /*
> >  * XXX: for !CONFIG_CPU_HAS_ADDRESS_SPACES this really needs to 
> > check
> >  * for TASK_SIZE!
> > +* Removing this helper is probably sufficient.
> >  */
>
> Shouldn't the above comment block be removed completely,
> as this is now implemented below?

Yes, obviously. Fixed now.

> > -   return 1;
> > +   if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES))
> > +   return 1;

I just noticed this should have the same change that I made for the
generic version, changed it now to

+   if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES) ||
+   !IS_ENABLED(CONFIG_MMU))

This is gone again after the cleanup patch, when the generic version
is used instead.

> > +   return (size <= limit) && (addr <= (limit - size));
> >  }
>
> Any pesky compilers that warn (or worse with -Werror) about
> "condition always true" for TASK_SIZE = 0xUL?

No, using a local variable avoids this warning.

Arnd

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Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire

2022-02-18 Thread Geert Uytterhoeven 
Hi Arnd,

On Wed, Feb 16, 2022 at 2:17 PM Arnd Bergmann  wrote:
> From: Arnd Bergmann 
>
> While most m68k platforms use separate address spaces for user
> and kernel space, at least coldfire does not, and the other
> ones have a TASK_SIZE that is less than the entire 4GB address
> range.
>
> Using the default implementation of __access_ok() stops coldfire
> user space from trivially accessing kernel memory.
>
> Signed-off-by: Arnd Bergmann 

Thanks for your patch!

> --- a/arch/m68k/include/asm/uaccess.h
> +++ b/arch/m68k/include/asm/uaccess.h
> @@ -12,14 +12,21 @@
>  #include 
>
>  /* We let the MMU do all checking */
> -static inline int access_ok(const void __user *addr,
> +static inline int access_ok(const void __user *ptr,
> unsigned long size)
>  {
> +   unsigned long limit = TASK_SIZE;
> +   unsigned long addr = (unsigned long)ptr;
> +
> /*
>  * XXX: for !CONFIG_CPU_HAS_ADDRESS_SPACES this really needs to check
>  * for TASK_SIZE!
> +* Removing this helper is probably sufficient.
>  */

Shouldn't the above comment block be removed completely,
as this is now implemented below?

> -   return 1;
> +   if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES))
> +   return 1;
> +
> +   return (size <= limit) && (addr <= (limit - size));
>  }

Any pesky compilers that warn (or worse with -Werror) about
"condition always true" for TASK_SIZE = 0xUL?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire

2022-02-17 Thread Christoph Hellwig 
Looks good,

Reviewed-by: Christoph Hellwig 

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