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
