Messages in this thread | | | Subject | Re: [RFC][PATCH 13/24] x86/pti: Extend PTI user mappings | From | Alexandre Chartre <> | Date | Mon, 9 Nov 2020 18:52:55 +0100 |
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On 11/9/20 6:28 PM, Andy Lutomirski wrote: > On Mon, Nov 9, 2020 at 3:22 AM Alexandre Chartre > <alexandre.chartre@oracle.com> wrote: >> >> Extend PTI user mappings so that more kernel entry code can be executed >> with the user page-table. To do so, we need to map syscall and interrupt >> entry code, > > Probably fine. > >> per cpu offsets (__per_cpu_offset, which is used some in >> entry code), > > This likely already leaks due to vulnerable CPUs leaking address space > layout info.
I forgot to update the comment, I am not mapping __per_cpu_offset anymore.
However, if we do map __per_cpu_offset then we don't need to enforce the ordering in paranoid_entry to switch CR3 before GS.
> >> the stack canary, > > That's going to be a very tough sell. >
I can get rid of this, but this will require to disable stack-protector for any function that we can call while using the user page-table, like already done in patch 21 (x86/entry: Disable stack-protector for IST entry C handlers).
alex.
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