Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering usingBPF

[Oleg Nesterov]

On 01/12, 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.

May be this needs something like LSM_UNSAFE_SECCOMP, or perhaps
cap_bprm_set_creds() should take seccomp.mode == 2 into account, I dunno.

OTOH, currently seccomp.mode == 1 doesn't allow to exec at all.

Oleg.

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