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Date:   Thu, 27 Aug 2020 11:15:12 -0700
From:   Linus Torvalds <>
To:     Christoph Hellwig <>
Cc:     Al Viro <>,
        Michael Ellerman <>,
        "the arch/x86 maintainers" <>,
        Kees Cook <>,
        Linux Kernel Mailing List <>,
        linux-fsdevel <>,
        linux-arch <>,
        linuxppc-dev <>
Subject: Re: [PATCH 08/10] x86: remove address space overrides using set_fs()

On Thu, Aug 27, 2020 at 8:00 AM Christoph Hellwig <> wrote:
>  SYM_FUNC_START(__get_user_2)
>         add $1,%_ASM_AX
>         jc bad_get_user

This no longer makes sense, and

> -       mov PER_CPU_VAR(current_task), %_ASM_DX
> -       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
> +       cmp %_ASM_DX,%_ASM_AX

This should be

        cmp %_ASM_DX,%_ASM_AX

instead (and then because we no longer modify _ASM_AX, we'd also
remove the offset on the access).

>  SYM_FUNC_START(__put_user_2)
> -       ENTER
> -       mov TASK_addr_limit(%_ASM_BX),%_ASM_BX
>         sub $1,%_ASM_BX

It's even more obvious here. We load a constant and then immediately
do a "sub $1" on that value.

It's not a huge deal, you don't have to respin the series for this, I
just wanted to point it out so that people are aware of it and if I
forget somebody else will hopefully remember that "we should fix that


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