Messages in this thread | | | Date | Tue, 7 Apr 2020 09:38:30 +0200 | From | Christoph Hellwig <> | Subject | Re: hv_hypercall_pg page permissios |
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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.
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