Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire
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- To: Arnd Bergmann <arnd@xxxxxxxxxx>
- Subject: Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire
- From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
- Date: Fri, 18 Feb 2022 10:00:39 +0100
- Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxx>, Linux-Arch <linux-arch@xxxxxxxxxxxxxxx>, Linux MM <linux-mm@xxxxxxxxx>, Linux API <linux-api@xxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, Brian Cain <bcain@xxxxxxxxxxxxxx>, Michal Simek <monstr@xxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, Nick Hu <nickhu@xxxxxxxxxxxxx>, Greentime Hu <green.hu@xxxxxxxxx>, Dinh Nguyen <dinguyen@xxxxxxxxxx>, Stafford Horne <shorne@xxxxxxxxx>, Helge Deller <deller@xxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Mark Rutland <mark.rutland@xxxxxxx>, Heiko Carstens <hca@xxxxxxxxxxxxx>, Rich Felker <dalias@xxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Richard Weinberger <richard@xxxxxx>, "the arch/x86 maintainers" <x86@xxxxxxxxxx>, Max Filippov <jcmvbkbc@xxxxxxxxx>, "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Ard Biesheuvel <ardb@xxxxxxxxxx>, alpha <linux-alpha@xxxxxxxxxxxxxxx>, arcml <linux-snps-arc@xxxxxxxxxxxxxxxxxxx>, linux-csky@xxxxxxxxxxxxxxx, "open list:QUALCOMM HEXAGON..." <linux-hexagon@xxxxxxxxxxxxxxx>, "linux-ia64@xxxxxxxxxxxxxxx" <linux-ia64@xxxxxxxxxxxxxxx>, linux-m68k <linux-m68k@xxxxxxxxxxxxxxx>, "open list:BROADCOM NVRAM DRIVER" <linux-mips@xxxxxxxxxxxxxxx>, Openrisc <openrisc@xxxxxxxxxxxxxxxxxxxx>, Parisc List <linux-parisc@xxxxxxxxxxxxxxx>, linuxppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>, linux-riscv <linux-riscv@xxxxxxxxxxxxxxxxxxx>, linux-s390 <linux-s390@xxxxxxxxxxxxxxx>, Linux-sh list <linux-sh@xxxxxxxxxxxxxxx>, sparclinux <sparclinux@xxxxxxxxxxxxxxx>, linux-um <linux-um@xxxxxxxxxxxxxxxxxxx>, "open list:TENSILICA XTENSA PORT (xtensa)" <linux-xtensa@xxxxxxxxxxxxxxxx>
- In-reply-to: <20220216131332.1489939-11-arnd@kernel.org>
- References: <20220216131332.1489939-1-arnd@kernel.org> <20220216131332.1489939-11-arnd@kernel.org>
Hi Arnd,
On Wed, Feb 16, 2022 at 2:17 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> 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@xxxxxxxx>
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@xxxxxxxxxxxxxx
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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