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    SubjectRe: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF
    On Thu, Jan 12, 2012 at 7:43 AM, Steven Rostedt <> 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?
    > Maybe I don't understand this correctly.

    Time to resurrect execve_nosecurity? If so, then the rule could be
    simplified to: seccomp programs cannot use normal execve at all.

    The longer I linger on lists and see neat ideas like this, the more I
    get annoyed that execve is magical. I dream of a distribution that
    doesn't use setuid, file capabilities, selinux transitions on exec, or
    any other privilege changes on exec *at all*. I think that the only
    things missing in the kernel (other than something intelligent to do
    about SELinux) are execve_nosecurity and the ability for a normal
    program to wait for an unrelated program to finish (or some other way
    that a program can ask a daemon to spawn a privileged program for it
    and then to cleanly wait for that program to finish in a way that
    could survive re-exec of the daemon).


    > -- Steve
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