[PATCH 2/2] Notify container-init parent a 'reboot' occured

Daniel Lezcano
2011-08-11T20:25:00Z

When the reboot syscall is called and the pid namespace where the calling
process belongs to is not from the init pidns, we send a SIGCHLD with CLD_REBOOTED
to the parent of this pid namespace.

Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
---
include/asm-generic/siginfo.h | 3 ++-
include/linux/sched.h | 1 +
kernel/signal.c | 40 ++++++++++++++++++++++++++++++++++++++++
kernel/sys.c | 20 ++++++++++++++++++--
4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h
index 0dd4e87..9bff4a2 100644
--- a/include/asm-generic/siginfo.h
+++ b/include/asm-generic/siginfo.h
@@ -218,7 +218,8 @@ typedef struct siginfo {
#define CLD_TRAPPED (__SI_CHLD|4) /* traced child has trapped */
#define CLD_STOPPED (__SI_CHLD|5) /* child has stopped */
#define CLD_CONTINUED (__SI_CHLD|6) /* stopped child has continued */
-#define NSIGCHLD 6
+#define CLD_REBOOTED (__SI_CHLD|7) /* process was killed by a reboot */
+#define NSIGCHLD 7

/*
* SIGPOLL si_codes
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 20b03bf..c62dc9e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2170,6 +2170,7 @@ extern int kill_pgrp(struct pid *pid, int sig, int priv);
extern int kill_pid(struct pid *pid, int sig, int priv);
extern int kill_proc_info(int, struct siginfo *, pid_t);
extern __must_check bool do_notify_parent(struct task_struct *, int);
+extern void do_notify_parent_cldreboot(struct task_struct *, int, char *);
extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
extern void force_sig(int, struct task_struct *);
extern int send_sig(int, struct task_struct *, int);
diff --git a/kernel/signal.c b/kernel/signal.c
index 291c970..7d3d44c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1668,6 +1668,46 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
return autoreap;
}

+void do_notify_parent_cldreboot(struct task_struct *tsk, int why, char *buffer)
+{
+ struct siginfo info = { };
+ struct task_struct *parent;
+ struct sighand_struct *sighand;
+ unsigned long flags;
+
+ if (tsk->ptrace)
+ parent = tsk->parent;
+ else {
+ tsk = tsk->group_leader;
+ parent = tsk->real_parent;
+ }
+
+ info.si_signo = SIGCHLD;
+ info.si_errno = 0;
+ info.si_status = why;
+
+ rcu_read_lock();
+ info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
+ info.si_uid = __task_cred(tsk)->uid;
+ rcu_read_unlock();
+
+ info.si_utime = cputime_to_clock_t(tsk->utime);
+ info.si_stime = cputime_to_clock_t(tsk->stime);
+
+ info.si_code = CLD_REBOOTED;
+
+ sighand = parent->sighand;
+ spin_lock_irqsave(&sighand->siglock, flags);
+ if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
+ sighand->action[SIGCHLD-1].sa.sa_flags & SA_CLDREBOOT)
+ __group_send_sig_info(SIGCHLD, &info, parent);
+ /*
+ * Even if SIGCHLD is not generated, we must wake up wait4 calls.
+ */
+ __wake_up_parent(tsk, parent);
+ spin_unlock_irqrestore(&sighand->siglock, flags);
+}
+
/**
* do_notify_parent_cldstop - notify parent of stopped/continued state change
* @tsk: task reporting the state change
diff --git a/kernel/sys.c b/kernel/sys.c
index a101ba3..8f7a9ed 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -42,6 +42,7 @@
#include <linux/syscalls.h>
#include <linux/kprobes.h>
#include <linux/user_namespace.h>
+#include <linux/sched.h>

#include <linux/kmsg_dump.h>

@@ -411,6 +412,13 @@ void kernel_power_off(void)
}
EXPORT_SYMBOL_GPL(kernel_power_off);

+static void pid_namespace_reboot(struct pid_namespace *pid_ns,
+ int cmd, char *buffer)
+{
+ struct task_struct *tsk = pid_ns->child_reaper;
+ do_notify_parent_cldreboot(tsk, cmd, buffer);
+}
+
static DEFINE_MUTEX(reboot_mutex);

/*
@@ -426,10 +434,18 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
{
char buffer[256];
int ret = 0;
+ struct pid_namespace *pid_ns = current->nsproxy->pid_ns;
+
+ /* We only trust the superuser with rebooting the system. */
+ if (!capable(CAP_SYS_BOOT)) {
+ /* If we are not in the initial pid namespace, we send a signal
+ * to the parent of this init pid namespace, notifying a shutdown
+ * occured */
+ if (pid_ns != &init_pid_ns)
+ pid_namespace_reboot(pid_ns, cmd, buffer);

- /* We only trust the superuser with rebooting the system. */
- if (!capable(CAP_SYS_BOOT))
return -EPERM;
+ }

/* For safety, we require "magic" arguments. */
if (magic1 != LINUX_REBOOT_MAGIC1 ||
--
1.7.4.1