[Devel] [PATCH 1/4] signal: Introduce kill_pid_ns_info

[Eric W. Biederman]

Implement the basic helper function that walks all of the processes in
a pid namespace and sends them all a signal. 

Both locations that could use this functions are also updated to use
this function.

I use find_ge_pid instead of for_each_process because it has a chance
of not touching every process in the system.

Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
---
 include/linux/sched.h  |    2 +
 kernel/pid_namespace.c |   17 +--------------
 kernel/signal.c        |   54 +++++++++++++++++++++++++++++++++++------------
 3 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index cda9ee9..eef3c22 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1665,6 +1665,8 @@ extern void release_task(struct task_struct * p);
 extern int send_sig_info(int, struct siginfo *, struct task_struct *);
 extern int force_sigsegv(int, struct task_struct *);
 extern int force_sig_info(int, struct siginfo *, struct task_struct *);
+extern int __kill_pid_ns_info(int sig, struct siginfo *info, struct pid_namespace *ns);
+extern int kill_pid_ns_info(int sig, struct siginfo *info, struct pid_namespace *ns);
 extern int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp);
 extern int kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp);
 extern int kill_pid_info(int sig, struct siginfo *info, struct pid *pid);
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 739a72b..67ba069 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -178,29 +178,14 @@ void free_pid_ns(struct kref *kref)
 
 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 {
-	int nr;
 	int rc;
 
 	/*
 	 * The last thread in the cgroup-init thread group is terminating.
 	 * Find remaining pid_ts in the namespace, signal and wait for them
 	 * to exit.
-	 *
-	 * Note:  This signals each threads in the namespace - even those that
-	 * 	  belong to the same thread group, To avoid this, we would have
-	 * 	  to walk the entire tasklist looking a processes in this
-	 * 	  namespace, but that could be unnecessarily expensive if the
-	 * 	  pid namespace has just a few processes. Or we need to
-	 * 	  maintain a tasklist for each pid namespace.
-	 *
 	 */
-	read_lock(&tasklist_lock);
-	nr = next_pidmap(pid_ns, 1);
-	while (nr > 0) {
-		kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
-		nr = next_pidmap(pid_ns, nr);
-	}
-	read_unlock(&tasklist_lock);
+	kill_pid_ns_info(SIGKILL, SEND_SIG_PRIV, pid_ns);
 
 	do {
 		clear_thread_flag(TIF_SIGPENDING);
diff --git a/kernel/signal.c b/kernel/signal.c
index 074905f..1eb0661 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1083,6 +1083,45 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 	return ret;
 }
 
+int __kill_pid_ns_info(int sig, struct siginfo *info, struct pid_namespace *ns)
+{
+	int retval = 0, count = 0;
+	struct task_struct *p;
+	struct pid *pid;
+	int nr;
+
+	/* Since there isn't a pid namespace list of tasks use the closet
+	 * approximation we have: find_ge_pid.
+	 */
+	nr = 0;
+	while ((pid = find_ge_pid(nr + 1, ns))) {
+		int err;
+
+		nr = pid_nr_ns(pid, ns);
+		p = pid_task(pid, PIDTYPE_PID);
+		if (!p || (nr <= 1) || !thread_group_leader(p) ||
+		    same_thread_group(p, current))
+			continue;
+
+		err = group_send_sig_info(sig, info, p);
+		++count;
+		if (err != -EPERM)
+			retval = err;
+	}
+	return count ? retval : -ESRCH;
+}
+
+int kill_pid_ns_info(int sig, struct siginfo *info, struct pid_namespace *ns)
+{
+	int retval;
+
+	read_lock(&tasklist_lock);
+	retval = __kill_pid_ns_info(sig, info, ns);
+	read_unlock(&tasklist_lock);
+
+	return retval;
+}
+
 /*
  * kill_pgrp_info() sends a signal to a process group: this is what the tty
  * control characters do (^C, ^Z etc)
@@ -1204,20 +1243,7 @@ static int kill_something_info(int sig, struct siginfo *info, int pid)
 	if (!pid) {
 		ret = kill_pgrp_info(sig, info, task_pgrp(current));
 	} else if (pid == -1) {
-		int retval = 0, count = 0;
-		struct task_struct * p;
-
-		read_lock(&tasklist_lock);
-		for_each_process(p) {
-			if (p->pid > 1 && !same_thread_group(p, current)) {
-				int err = group_send_sig_info(sig, info, p);
-				++count;
-				if (err != -EPERM)
-					retval = err;
-			}
-		}
-		read_unlock(&tasklist_lock);
-		ret = count ? retval : -ESRCH;
+		ret = kill_pid_ns_info(sig, info, task_active_pid_ns(current));
 	} else if (pid < 0) {
 		ret = kill_pgrp_info(sig, info, find_vpid(-pid));
 	} else {
-- 
1.5.3.rc6.17.g1911

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