Messages in this thread | | | Date | Wed, 23 Aug 2017 18:04:43 +0100 | From | Mark Rutland <> | Subject | Re: [kernel-hardening] [PATCH v5 04/10] arm64: Add __flush_tlb_one() |
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On Wed, Aug 23, 2017 at 10:58:42AM -0600, Tycho Andersen wrote: > Hi Mark, > > On Mon, Aug 14, 2017 at 05:50:47PM +0100, Mark Rutland wrote: > > That said, is there any reason not to use flush_tlb_kernel_range() > > directly? > > So it turns out that there is a difference between __flush_tlb_one() and > flush_tlb_kernel_range() on x86: flush_tlb_kernel_range() flushes all the TLBs > via on_each_cpu(), where as __flush_tlb_one() only flushes the local TLB (which > I think is enough here).
That sounds suspicious; I don't think that __flush_tlb_one() is sufficient.
If you only do local TLB maintenance, then the page is left accessible to other CPUs via the (stale) kernel mappings. i.e. the page isn't exclusively mapped by userspace.
Thanks, Mark.
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