Hi, IIUC, LSMs are supposed to give us the ability to design policy around unprivileged users and in addition to privileged users. As we expand our usage of BPF LSM's, there are cases where we want to restrict privileged users from unloading our progs. For instance, any privileged user that wants to remove restrictions we've placed on privileged users. We currently have a loader application doesn't leverage BPF skeletons. We instead load BPF object files, and then pin the progs to a mount point that is a bpf filesystem. On next run, if we have new policies, load in new policies, and finally unload the old. Here are some conditions a privileged user may unload programs: umount /sys/fs/bpf rm -rf /sys/fs/bpf/lsm rm /sys/fs/bpf/lsm/some_prog unlink /sys/fs/bpf/lsm/some_prog This works because once we remove the last reference, the programs and pinned maps are cleaned up. Moving individual pins or moving the mount entirely with mount --move do not perform any clean up operations. Lastly, bpftool doesn't currently have the ability to unload LSM's AFAIK. The few ideas I have floating around are: 1. Leverage some LSM hooks (BPF or otherwise) to restrict on the functions security_sb_umount(), security_path_unlink(), security_inode_unlink(). Both security_path_unlink() and security_inode_unlink() handle the unlink/remove case, but not the umount case. 3. Leverage SELinux/Apparmor to possibly handle these cases. 4. Introduce a security_bpf_prog_unload() to target hopefully the umount and unlink cases at the same time. 5. Possible moonshot idea: introduce a interface to pin _specifically_ BPF LSM's to the kernel, and avoid the bpf sysfs problems all together. We're making the assumption this problem has been thought about before, and are wondering if there's anything obvious we're missing here. Fred
