Re: [Qemu-devel] [PATCHv4 6/6] seccomp: adding documentation to new seccomp model

[Daniel P. Berrange]

On Fri, Sep 01, 2017 at 12:58:18PM +0200, Eduardo Otubo wrote:
> Adding new documentation under docs/ to describe every one and each new
> option added by the refactoring patchset.
> 
> Signed-off-by: Eduardo Otubo <address@hidden>
> ---
>  docs/seccomp.txt | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>  create mode 100644 docs/seccomp.txt
> 
> diff --git a/docs/seccomp.txt b/docs/seccomp.txt
> new file mode 100644
> index 0000000000..a5eca85a9b
> --- /dev/null
> +++ b/docs/seccomp.txt
> @@ -0,0 +1,31 @@
> +QEMU Seccomp system call filter
> +===============================
> +
> +Starting from QEMU version 2.11, the seccomp filter does not work as a
> +whitelist but as a blacklist instead. This method allows safer deploys since
> +only the strictly forbidden system calls will be black-listed and the
> +possibility of breaking any workload is close to zero.
> +
> +The default option (-sandbox on) has a slightly looser security though and 
> the
> +reason is that it shouldn't break any backwards compatibility with previous
> +deploys and command lines already running. But if the intent is to have a
> +better security from this version on, one should make use of the following
> +additional options properly:
> +
> +* obsolete=allow|deny: It allows Qemu to run safely on old system that still
> +  relies on old system calls.
> +
> +* elevateprivileges=allow|deny|children: It allows or denies Qemu process
> +  to elevate its privileges by blacklisting all set*uid|gid system calls. The
> +  'children' option sets the PR_SET_NO_NEW_PRIVS to 1 which allows helpers
> +  (forks and execs) to run unprivileged.
> +
> +* spawn=allow|deny: It blacklists fork and execve system calls, avoiding 
> QEMU to
> +  spawn new threads or processes.
> +
> +* resourcecontrol=allow|deny: It blacklists all process affinity and 
> scheduler
> +  priority system calls to avoid that the process can increase its amount of
> +  allowed resource consumption.
> +

This ought to be part of qemu-options.hx so it makes it into the qemu
docs & man page.

Regards,
Daniel
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