linux-kernel - hv_hypercall_pg page permissios

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Message-ID: <20200407065500.GA28490@lst.de>
Date:   Tue, 7 Apr 2020 08:55:00 +0200
From:   Christoph Hellwig <hch@....de>
To:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: hv_hypercall_pg page permissios

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..