Quoting Daniel P. Berrange (berrange@xxxxxxxxxx): > From: "Daniel P. Berrange" <berrange@xxxxxxxxxx> > > The following commit > > commit cf3f89214ef6a33fad60856bc5ffd7bb2fc4709b > Author: Daniel Lezcano <daniel.lezcano@xxxxxxx> > Date: Wed Mar 28 14:42:51 2012 -0700 > > pidns: add reboot_pid_ns() to handle the reboot syscall > > introduced custom handling of the reboot() syscall when invoked > from a non-initial PID namespace. The intent was that a process > in a container can be allowed to keep CAP_SYS_BOOT and execute > reboot() to shutdown/reboot just their private container, rather > than the host. > > Unfortunately the kexec_load() syscall also relies on the > CAP_SYS_BOOT capability. So by allowing a container to keep > this capability to safely invoke reboot(), they mistakenly > also gain the ability to use kexec_load(). The solution is > to make kexec_load() return -EPERM if invoked from a PID > namespace that is not the initial namespace > > Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx> > Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> (Please see my previous email explaining why I believe the pidns is an appropriate check) > Cc: Daniel Lezcano <daniel.lezcano@xxxxxxx> > Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > Cc: Tejun Heo <tj@xxxxxxxxxx> > Cc: Oleg Nesterov <oleg@xxxxxxxxxx> > --- > kernel/kexec.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/kexec.c b/kernel/kexec.c > index 0668d58..b152bde 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -947,6 +947,11 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, > if (!capable(CAP_SYS_BOOT)) > return -EPERM; > > + /* Processes in containers must not be allowed to load a new > + * kernel, even if they have CAP_SYS_BOOT */ > + if (task_active_pid_ns(current) != &init_pid_ns) > + return -EPERM; > + > /* > * Verify we have a legal set of flags > * This leaves us room for future extensions. > -- > 1.7.11.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
