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    SubjectRe: seccomp feature development
    On Tue, May 19, 2020 at 12:48:46PM +1000, Aleksa Sarai wrote:
    > On 2020-05-19, Jann Horn <jannh@google.com> wrote:
    > > On Mon, May 18, 2020 at 11:05 PM Kees Cook <keescook@chromium.org> wrote:
    > > > ## deep argument inspection
    > > >
    > > > Background: seccomp users would like to write filters that traverse
    > > > the user pointers passed into many syscalls, but seccomp can't do this
    > > > dereference for a variety of reasons (mostly involving race conditions and
    > > > rearchitecting the entire kernel syscall and copy_from_user() code flows).
    > >
    > > Also, other than for syscall entry, it might be worth thinking about
    > > whether we want to have a special hook into seccomp for io_uring.
    > > io_uring is growing support for more and more syscalls, including
    > > things like openat2, connect, sendmsg, splice and so on, and that list
    > > is probably just going to grow in the future. If people start wanting
    > > to use io_uring in software with seccomp filters, it might be
    > > necessary to come up with some mechanism to prevent io_uring from
    > > permitting access to almost everything else...
    > >
    > > Probably not a big priority for now, but something to keep in mind for
    > > the future.
    >
    > Indeed. Quite a few people have raised concerns about io_uring and its
    > debug-ability, but I agree that another less-commonly-mentioned concern
    > should be how you restrict io_uring(2) from doing operations you've
    > disallowed through seccomp. Though obviously user_notif shouldn't be
    > allowed. :D

    As soon as you switch kernels to an io_uring supported kernel while
    maintaing a blacklist without updating all your seccomp filters you're
    currently hosed (Yes, blacklists aren't great but they have their
    uses.).

    Christian

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