On Fri, Feb 18, 2022 at 10:00 AM Geert Uytterhoeven
[off-list ref] wrote:

quoted

 /* 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.

quoted

-       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.

quoted

+       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