Messages in this thread | | | Date | Thu, 11 Aug 2016 00:06:45 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 2/2] arm: apply more __ro_after_init |
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On Wed, Aug 10, 2016 at 09:41:23PM +0200, Arnd Bergmann wrote: > It might be better to start by making the fixed mapping readonly, > as KASLR doesn't protect that one at all, and change the TLS > code accordingly.
I think that's impossible, because we gave userspace permission to read 0xffff0ff0 directly without using __kuser_get_tls. You're talking about potentially breaking userspace.
If you disable kuser helpers, then the page becomes read-only and invisible to userspace anyway. So, everything is being done there which can be done - if you have kuser helpers enabled, then you lose some opportunities for these security improvements.
-- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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