linux-kernel - Re: [PATCH 0/6] Memory Mapping (VMA) protection using PKU

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Message-ID: <CABi2SkUzwdBGyjHjXtyFK5dtLVB2keKCpZpkpiuaStd6b2cEWA@mail.gmail.com>
Date:   Wed, 24 May 2023 13:15:50 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Jeff Xu <jeffxu@...gle.com>,
        Stephen Röttger <sroettger@...gle.com>,
        luto@...nel.org, jorgelo@...omium.org, keescook@...omium.org,
        groeck@...omium.org, jannh@...gle.com, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-mm@...ck.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 0/6] Memory Mapping (VMA) protection using PKU - set 1

Thanks for bringing this to my attention. Regarding io_uring:
>
> io_uring fundamentally doesn't have the same checks.  The kernel side
> work can be done from an asynchronous kernel thread.  That kernel thread
> doesn't have a meaningful PKRU value.  The register has a value, but
> it's not really related to the userspace threads that are sending it
> requests.
>

I asked the question to the io_uring list [1].  io_uring thread will
respect PKRU of the user thread, async or not,  the behavior is the
same as regular syscall. There will be no issue for io_uring, i.e if
it decides to add more memory mapping syscalls to supported cmd in
future.

[1] https://lore.kernel.org/io-uring/CABi2SkUp45HEt7eQ6a47Z7b3LzW=4m3xAakG35os7puCO2dkng@mail.gmail.com/

Thanks.
-Jeff