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    SubjectRe: [PATCH 0/4 POC] Allow executing code and syscalls in another address space
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    On Wed, 2021-04-14 at 08:22 +0100, Anton Ivanov wrote:
    > On 14/04/2021 06:52, Andrei Vagin wrote:
    > > We already have process_vm_readv and process_vm_writev to read and write
    > > to a process memory faster than we can do this with ptrace. And now it
    > > is time for process_vm_exec that allows executing code in an address
    > > space of another process. We can do this with ptrace but it is much
    > > slower.
    > >
    > > = Use-cases =
    > >
    > > Here are two known use-cases. The first one is “application kernel”
    > > sandboxes like User-mode Linux and gVisor. In this case, we have a
    > > process that runs the sandbox kernel and a set of stub processes that
    > > are used to manage guest address spaces. Guest code is executed in the
    > > context of stub processes but all system calls are intercepted and
    > > handled in the sandbox kernel. Right now, these sort of sandboxes use
    > > PTRACE_SYSEMU to trap system calls, but the process_vm_exec can
    > > significantly speed them up.
    >
    > Certainly interesting, but will require um to rework most of its memory
    > management and we will most likely need extra mm support to make use of
    > it in UML. We are not likely to get away just with one syscall there.

    Might help the seccomp mode though:

    https://patchwork.ozlabs.org/project/linux-um/list/?series=231980

    johannes


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