Re: [PATCH v2 10/18] m68k: fix access_ok for coldfire
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2022-02-18 09:00:58
Also in:
linux-alpha, linux-arch, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, linuxppc-dev, lkml, sparclinux
Hi Arnd, On Wed, Feb 16, 2022 at 2:17 PM Arnd Bergmann [off-list ref] 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!
quoted hunk ↗ jump to hunk
--- 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