On Thu, Oct 10, 2019 at 02:45:38PM -0700, Kees Cook wrote: > On Fri, Sep 20, 2019 at 10:30:05AM +0200, Christian Brauner wrote: > > + * Similar precautions should be applied when stacking SECCOMP_RET_USER_NOTIF. > > + * For SECCOMP_RET_USER_NOTIF filters acting on the same syscall the uppermost > > + * filter takes precedence. This means that the uppermost > > + * SECCOMP_RET_USER_NOTIF filter can override any SECCOMP_IOCTL_NOTIF_SEND from > > + * lower filters essentially allowing all syscalls to pass by using > > + * SECCOMP_USER_NOTIF_FLAG_CONTINUE. Note that SECCOMP_RET_USER_NOTIF can > ^^^^^^^^^^^^^^ > This is meant to read RET_TRACE, yes? Yes. :) > > > + * equally be overriden by SECCOMP_USER_NOTIF_FLAG_CONTINUE. > > I rewrote this paragraph with that corrected and swapping some > "upper/lower" to "most recently added" etc: > > + * Similar precautions should be applied when stacking SECCOMP_RET_USER_NOTIF > + * or SECCOMP_RET_TRACE. For SECCOMP_RET_USER_NOTIF filters acting on the > + * same syscall, the most recently added filter takes precedence. This means > + * that the new SECCOMP_RET_USER_NOTIF filter can override any > + * SECCOMP_IOCTL_NOTIF_SEND from earlier filters, essentially allowing all > + * such filtered syscalls to be executed by sending the response > + * SECCOMP_USER_NOTIF_FLAG_CONTINUE. Note that SECCOMP_RET_TRACE can equally > + * be overriden by SECCOMP_USER_NOTIF_FLAG_CONTINUE. > > > Ultimately, I think this caveat is fine. RET_USER_NOTIF and RET_TRACE are > both used from the "process manager" use-case. The benefits of "continue" > semantics here outweighs the RET_USER_NOTIF and RET_TRACE "bypass". If > we end up in a situation where we need to deal with some kind of > nesting where this is a problem in practice, we can revisit this. > > Applied to my for-next/seccomp. Thanks! Thanks! Christian
