linux-kernel - Re: properly support exec and wait with kernel pointers

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Date:   Mon, 15 Jun 2020 15:42:51 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: properly support exec and wait with kernel pointers

On Mon, Jun 15, 2020 at 3:00 PM Christoph Hellwig <hch@....de> wrote:
>
> Hi all,
>
> this series first cleans up the exec code and then adds proper
> kernel_execveat and kernel_wait callers instead of relying on the fact
> that the early init code and kernel threads implicitly run with
> the address limit set to KERNEL_DS.
>
> Note that the cleanup removes the compat execve(at) handlers (almost)
> entirely, as we can handle the compat difference very nicely in a
> unified codebase.  The only exception is x86 where this would list the
> handlers twice in the same syscall table due to the messed up x32
> design.  I had to add an extra compat handler just for that case, but
> maybe someone has a better idea.

I looked at all the patches and I like it a lot. I replied with some suggestions
for x32, but maybe I misunderstood what its problem is, as I don't see
anything preventing us from having two entries in the x32 table pointing
to the same function.

       Arnd