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In-Reply-To: <9d64c949-6d5f-06c0-47ef-caade67477e5@intel.com>
From:   Jeff Xu <jeffxu@chromium.org>
Date:   Wed, 24 May 2023 13:15:50 -0700
Message-ID: <CABi2SkUzwdBGyjHjXtyFK5dtLVB2keKCpZpkpiuaStd6b2cEWA@mail.gmail.com>
Subject: Re: [PATCH 0/6] Memory Mapping (VMA) protection using PKU - set 1
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Jeff Xu <jeffxu@google.com>,
        =?UTF-8?Q?Stephen_R=C3=B6ttger?= <sroettger@google.com>,
        luto@kernel.org, jorgelo@chromium.org, keescook@chromium.org,
        groeck@chromium.org, jannh@google.com, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-mm@kvack.org, linux-hardening@vger.kernel.org
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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