linux-kernel - Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access

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Date:   Wed, 29 Mar 2023 17:41:21 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Oleg Nesterov" <oleg@...hat.com>,
        "Gregory Price" <gourry.memverge@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Linux-Arch <linux-arch@...r.kernel.org>, avagin@...il.com,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Andy Lutomirski" <luto@...nel.org>, krisman@...labora.com,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Jonathan Corbet" <corbet@....net>, shuah <shuah@...nel.org>,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>,
        "Mark Rutland" <mark.rutland@....com>, tongtiangen@...wei.com,
        "Robin Murphy" <robin.murphy@....com>,
        "Gregory Price" <gregory.price@...verge.com>
Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok

On Wed, Mar 29, 2023, at 17:15, Oleg Nesterov wrote:
>
> This look as if access_ok() or __access_ok() doesn't depend on task, but
> this is not true in general. Say, TASK_SIZE_MAX can check is_32bit_task()
> test_thread_flag(TIF_32BIT...) and this uses "current".
>
> Again, we probably do not care, but I don't like the fact task_access_ok()
> looks as if task_access_ok(task) returns the same result as "task" calling
> access_ok().

I think the idea of TASK_SIZE_MAX is that it is a compile-time constant and in fact independent of current, while TASK_SIZE
takes TIF_32BIT into account.

     Arnd