[PATCH] add child reaper to pid_namespace

Add a per pid_namespace child-reaper.  This is needed so processes are reaped
within the same pid space and do not spill over to the parent pid space.  Its
also needed so containers preserve existing semantic that pid == 1 would reap
orphaned children.

This is based on Eric Biederman's patch: http://lkml.org/lkml/2006/2/6/285

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/exec.c b/fs/exec.c
index 60433e2254a44d692ac53021bd84d40a216f1fa9..12d8cd461b412378fe8d16b8e39c7a330770a649 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -38,6 +38,7 @@
 #include <linux/binfmts.h>
 #include <linux/swap.h>
 #include <linux/utsname.h>
+#include <linux/pid_namespace.h>
 #include <linux/module.h>
 #include <linux/namei.h>
 #include <linux/proc_fs.h>
@@ -620,8 +621,8 @@ static int de_thread(struct task_struct *tsk)
         * Reparenting needs write_lock on tasklist_lock,
         * so it is safe to do it under read_lock.
         */
-       if (unlikely(tsk->group_leader == child_reaper))
-               child_reaper = tsk;
+       if (unlikely(tsk->group_leader == child_reaper(tsk)))
+               tsk->nsproxy->pid_ns->child_reaper = tsk;
 
        zap_other_threads(tsk);
        read_unlock(&tasklist_lock);

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 2c0007d172189390911779471f54db752e3dd50d..4dec047b1837f1d7e365d1127dbbc68e4937d201 100644 (file)
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -35,8 +35,9 @@ enum pid_type
  *
  * Holding a reference to struct pid solves both of these problems.
  * It is small so holding a reference does not consume a lot of
- * resources, and since a new struct pid is allocated when the numeric
- * pid value is reused we don't mistakenly refer to new processes.
+ * resources, and since a new struct pid is allocated when the numeric pid
+ * value is reused (when pids wrap around) we don't mistakenly refer to new
+ * processes.
  */
 
 struct pid

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 76e7c6b2cf3304e003f7002597d7d6627c7a7f9c..d2a9d419f01f8903e12c4ab2da5e17a0d54f7481 100644 (file)
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -19,6 +19,7 @@ struct pid_namespace {
        struct kref kref;
        struct pidmap pidmap[PIDMAP_ENTRIES];
        int last_pid;
+       struct task_struct *child_reaper;
 };
 
 extern struct pid_namespace init_pid_ns;
@@ -36,4 +37,9 @@ static inline void put_pid_ns(struct pid_namespace *ns)
        kref_put(&ns->kref, free_pid_ns);
 }
 
+static inline struct task_struct *child_reaper(struct task_struct *tsk)
+{
+       return tsk->nsproxy->pid_ns->child_reaper;
+}
+
 #endif /* _LINUX_PID_NS_H */

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6fec1d419714dc3ea5bb908fb27dfc860f8606cc..f0317edea141124f4c00db87807642ebf22a5b1e 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1400,7 +1400,6 @@ extern NORET_TYPE void do_group_exit(int);
 extern void daemonize(const char *, ...);
 extern int allow_signal(int);
 extern int disallow_signal(int);
-extern struct task_struct *child_reaper;
 
 extern int do_execve(char *, char __user * __user *, char __user * __user *, struct pt_regs *);
 extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *);

diff --git a/init/main.c b/init/main.c
index 4cdcd06e6d7826bf1448204c4d9c1f430b12367e..036f97c0c34c80bf26a55079e69dcda8f7f0e37d 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -51,6 +51,7 @@
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
 #include <linux/utsrelease.h>
+#include <linux/pid_namespace.h>
 #include <linux/compile.h>
 
 #include <asm/io.h>
@@ -626,8 +627,6 @@ static int __init initcall_debug_setup(char *str)
 }
 __setup("initcall_debug", initcall_debug_setup);
 
-struct task_struct *child_reaper = &init_task;
-
 extern initcall_t __initcall_start[], __initcall_end[];
 
 static void __init do_initcalls(void)
@@ -727,7 +726,7 @@ static int init(void * unused)
         * assumptions about where in the task array this
         * can be found.
         */
-       child_reaper = current;
+       init_pid_ns.child_reaper = current;
 
        cad_pid = task_pid(current);
 

diff --git a/kernel/exit.c b/kernel/exit.c
index 28d9feedfd27a4633f68e172f8ab83c78e827116..fd0e067952ab03fc3e188913d6c3e575de6d1862 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -22,6 +22,7 @@
 #include <linux/file.h>
 #include <linux/binfmts.h>
 #include <linux/nsproxy.h>
+#include <linux/pid_namespace.h>
 #include <linux/ptrace.h>
 #include <linux/profile.h>
 #include <linux/mount.h>
@@ -48,7 +49,6 @@
 #include <asm/mmu_context.h>
 
 extern void sem_exit (void);
-extern struct task_struct *child_reaper;
 
 static void exit_mm(struct task_struct * tsk);
 
@@ -260,7 +260,8 @@ static int has_stopped_jobs(int pgrp)
 }
 
 /**
- * reparent_to_init - Reparent the calling kernel thread to the init task.
+ * reparent_to_init - Reparent the calling kernel thread to the init task
+ * of the pid space that the thread belongs to.
  *
  * If a kernel thread is launched as a result of a system call, or if
  * it ever exits, it should generally reparent itself to init so that
@@ -278,8 +279,8 @@ static void reparent_to_init(void)
        ptrace_unlink(current);
        /* Reparent to init */
        remove_parent(current);
-       current->parent = child_reaper;
-       current->real_parent = child_reaper;
+       current->parent = child_reaper(current);
+       current->real_parent = child_reaper(current);
        add_parent(current);
 
        /* Set the exit signal to SIGCHLD so we signal init on exit */
@@ -662,7 +663,8 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
  * When we die, we re-parent all our children.
  * Try to give them to another thread in our thread
  * group, and if no such member exists, give it to
- * the global child reaper process (ie "init")
+ * the child reaper process (ie "init") in our pid
+ * space.
  */
 static void
 forget_original_parent(struct task_struct *father, struct list_head *to_release)
@@ -673,7 +675,7 @@ forget_original_parent(struct task_struct *father, struct list_head *to_release)
        do {
                reaper = next_thread(reaper);
                if (reaper == father) {
-                       reaper = child_reaper;
+                       reaper = child_reaper(father);
                        break;
                }
        } while (reaper->exit_state);
@@ -859,8 +861,13 @@ fastcall NORET_TYPE void do_exit(long code)
                panic("Aiee, killing interrupt handler!");
        if (unlikely(!tsk->pid))
                panic("Attempted to kill the idle task!");
-       if (unlikely(tsk == child_reaper))
-               panic("Attempted to kill init!");
+       if (unlikely(tsk == child_reaper(tsk))) {
+               if (tsk->nsproxy->pid_ns != &init_pid_ns)
+                       tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
+               else
+                       panic("Attempted to kill init!");
+       }
+
 
        if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
                current->ptrace_message = code;

diff --git a/kernel/pid.c b/kernel/pid.c
index 1d9cc268b499e630b1762afcc722fe834b391f55..2efe9d8d367b9346e1a38bc92027f0a24345029d 100644 (file)
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -65,7 +65,8 @@ struct pid_namespace init_pid_ns = {
        .pidmap = {
                [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
        },
-       .last_pid = 0
+       .last_pid = 0,
+       .child_reaper = &init_task
 };
 
 /*

diff --git a/kernel/signal.c b/kernel/signal.c
index 9eac4db60eda21a4e6b134fbd21eaca46fbfc2a1..1921ffdc5e777eee98081639ff6960b9baf49010 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -24,6 +24,9 @@
 #include <linux/signal.h>
 #include <linux/capability.h>
 #include <linux/freezer.h>
+#include <linux/pid_namespace.h>
+#include <linux/nsproxy.h>
+
 #include <asm/param.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -1877,8 +1880,12 @@ relock:
                if (sig_kernel_ignore(signr)) /* Default is nothing. */
                        continue;
 
-               /* Init gets no signals it doesn't want.  */
-               if (current == child_reaper)
+               /*
+                * Init of a pid space gets no signals it doesn't want from
+                * within that pid space. It can of course get signals from
+                * its parent pid space.
+                */
+               if (current == child_reaper(current))
                        continue;
 
                if (sig_kernel_stop(signr)) {