diff mbox series

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

Message ID 20220216131332.1489939-11-arnd@kernel.org (mailing list archive)
State New
Headers show
Series clean up asm/uaccess.h, kill set_fs for good | expand

Commit Message

Arnd Bergmann Feb. 16, 2022, 1:13 p.m. UTC
From: Arnd Bergmann <arnd@arndb.de>

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 <arnd@arndb.de>
---
 arch/m68k/include/asm/uaccess.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Comments

Christoph Hellwig Feb. 18, 2022, 6:30 a.m. UTC | #1
Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
Geert Uytterhoeven Feb. 18, 2022, 9 a.m. UTC | #2
Hi Arnd,

On Wed, Feb 16, 2022 at 2:17 PM Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> 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 <arnd@arndb.de>

Thanks for your patch!

> --- a/arch/m68k/include/asm/uaccess.h
> +++ b/arch/m68k/include/asm/uaccess.h
> @@ -12,14 +12,21 @@
>  #include <asm/extable.h>
>
>  /* 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 = 0xFFFFFFFFUL?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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
Arnd Bergmann Feb. 18, 2022, 9:24 a.m. UTC | #3
On Fri, Feb 18, 2022 at 10:00 AM Geert Uytterhoeven
<geert@linux-m68k.org> 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 = 0xFFFFFFFFUL?

No, using a local variable avoids this warning.

        Arnd
diff mbox series

Patch

diff --git a/arch/m68k/include/asm/uaccess.h b/arch/m68k/include/asm/uaccess.h
index 79617c0b2f91..8eb625e75452 100644
--- a/arch/m68k/include/asm/uaccess.h
+++ b/arch/m68k/include/asm/uaccess.h
@@ -12,14 +12,21 @@ 
 #include <asm/extable.h>
 
 /* 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.
 	 */
-	return 1;
+	if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES))
+		return 1;
+
+	return (size <= limit) && (addr <= (limit - size));
 }
 
 /*