From: Christoph Hellwig <hch@lst.de>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
x86@kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org,
"K. Y. Srinivasan" <kys@microsoft.com>,
Stephen Hemminger <stephen@networkplumber.org>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: hv_hypercall_pg page permissios
Date: Tue, 7 Apr 2020 09:38:30 +0200 [thread overview]
Message-ID: <20200407073830.GA29279@lst.de> (raw)
In-Reply-To: <87v9mblpq6.fsf@vitty.brq.redhat.com>
On Tue, Apr 07, 2020 at 09:28:01AM +0200, Vitaly Kuznetsov wrote:
> Christoph Hellwig <hch@lst.de> writes:
>
> > Hi all,
> >
> > The x86 Hyper-V hypercall page (hv_hypercall_pg) is the only allocation
> > in the kernel using __vmalloc with exectutable persmissions, and the
> > only user of PAGE_KERNEL_RX. Is there any good reason it needs to
> > be readable? Otherwise we could use vmalloc_exec and kill off
> > PAGE_KERNEL_RX. Note that before 372b1e91343e6 ("drivers: hv: Turn off
> > write permission on the hypercall page") it was even mapped writable..
>
> [There is nothing secret in the hypercall page, by reading it you can
> figure out if you're running on Intel or AMD (VMCALL/VMMCALL) but it's
> likely not the only possible way :-)]
>
> I see no reason for hv_hypercall_pg to remain readable. I just
> smoke-tested
Thanks, I have the same in my WIP tree, but just wanted to confirm this
makes sense.
next prev parent reply other threads:[~2020-04-07 7:38 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 6:55 hv_hypercall_pg page permissios Christoph Hellwig
2020-04-07 7:28 ` Vitaly Kuznetsov
2020-04-07 7:38 ` Christoph Hellwig [this message]
2020-04-07 21:01 ` Andy Lutomirski
2020-06-12 7:48 ` Dexuan Cui
2020-06-15 8:35 ` Vitaly Kuznetsov
2020-06-15 17:41 ` Dexuan Cui
2020-06-15 19:49 ` Dexuan Cui
2020-06-16 7:23 ` Christoph Hellwig
2020-06-16 10:18 ` Peter Zijlstra
2020-06-16 10:23 ` Christoph Hellwig
2020-06-16 10:24 ` Christoph Hellwig
2020-06-16 10:31 ` Peter Zijlstra
2020-06-16 10:33 ` Christoph Hellwig
2020-06-16 10:40 ` Peter Zijlstra
2020-06-16 10:42 ` Christoph Hellwig
2020-06-16 10:52 ` Christoph Hellwig
2020-06-16 11:24 ` Peter Zijlstra
2020-06-16 14:39 ` Christoph Hellwig
2020-06-16 9:29 ` Vitaly Kuznetsov
2020-06-16 9:33 ` Christoph Hellwig
2020-06-16 9:55 ` Christoph Hellwig
2020-06-16 10:08 ` Christoph Hellwig
2020-06-16 10:50 ` Vitaly Kuznetsov
2020-06-16 10:20 ` Peter Zijlstra
2020-04-07 18:10 ` Dexuan Cui
2020-04-07 20:42 ` Wei Liu
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