[Maverick] request: CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

[Kees Cook]

Hi!

Could we enable this test, just to be safer during compiles? It won't
affect run-time, it just forces the build to be safer, IIUC:

arch/x86/include/asm/uaccess_32.h:

extern void copy_from_user_overflow(void)
#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
        __compiletime_error("copy_from_user() buffer size is not provably correct")
#else
        __compiletime_warning("copy_from_user() buffer size is not provably correct")
#endif

static inline unsigned long __must_check copy_from_user(void *to,
                                          const void __user *from,
                                          unsigned long n)
{
        int sz = __compiletime_object_size(to);

        if (likely(sz == -1 || sz >= n))
                n = _copy_from_user(to, from, n);
        else
                copy_from_user_overflow();

        return n;
}


-- 
Kees Cook
Ubuntu Security Team