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    SubjectRe: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF
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    On Thu, Jan 12, 2012 at 9:43 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
    > On Wed, 2012-01-11 at 11:25 -0600, Will Drewry wrote:
    >
    >> Filter programs may _only_ cross the execve(2) barrier if last filter
    >> program was attached by a task with CAP_SYS_ADMIN capabilities in its
    >> user namespace.  Once a task-local filter program is attached from a
    >> process without privileges, execve will fail.  This ensures that only
    >> privileged parent task can affect its privileged children (e.g., setuid
    >> binary).
    >
    > This means that a non privileged user can not run another program with
    > limited features? How would a process exec another program and filter
    > it? I would assume that the filter would need to be attached first and
    > then the execv() would be performed. But after the filter is attached,
    > the execv is prevented?

    Yeah - it means tasks can filter themselves, but not each other.
    However, you can inject a filter for any dynamically linked executable
    using LD_PRELOAD.

    > Maybe I don't understand this correctly.

    You're right on. This was to ensure that one process didn't cause
    crazy behavior in another. I think Alan has a better proposal than
    mine below. (Goes back to catching up.)
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