linux-kernel - Re: [RFC] minor kfence patches

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Message-ID: <CANpmjNMViC4thxCESfmj8j1ZWvNsz2oPSraPta3BAUQjFBoDtw@mail.gmail.com>
Date:   Fri, 14 May 2021 12:56:30 +0200
From:   Marco Elver <elver@...gle.com>
To:     Sven Schnelle <svens@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] minor kfence patches

On Fri, 14 May 2021 at 11:21, Sven Schnelle <svens@...ux.ibm.com> wrote:
>
> i'm currently looking into adding support for KFENCE to the s390
> architecture. So far everything is straightforward, and i get the
> kfence testsuite to pass, which is good! :)

Nice to see KFENCE being added to more architectures.

> One minor thing i encountered is that for a translation exception,
> s390 only reports the page address, but not the complete address. I
> worked around that by adding a function to kfence which allows to mask
> out certain bits during unit testing. I wonder whether that should be a
> weak function that can be implemented by architectures if required, some
> kconfig option, or some other way?

I've commented on the other patches.


Thanks,
-- Marco

> The other thing is that s390 (and some other architectures) has different
> address spaces for kernel and user space, so the decision whether an
> address belongs to user or kernel space cannot be made by just looking
> at the address. I added a small if (user_mode(regs)) check to
> kfence_handle_page_fault(). But this could of also be done in the
> architecture specific code.
>
> What do you think?
>
> Thanks,
> Sven
>
>