pid namespaces: changes to show virtual ids to user

This is the largest patch in the set. Make all (I hope) the places where
the pid is shown to or get from user operate on the virtual pids.

The idea is:
 - all in-kernel data structures must store either struct pid itself
   or the pid's global nr, obtained with pid_nr() call;
 - when seeking the task from kernel code with the stored id one
   should use find_task_by_pid() call that works with global pids;
 - when showing pid's numerical value to the user the virtual one
   should be used, but however when one shows task's pid outside this
   task's namespace the global one is to be used;
 - when getting the pid from userspace one need to consider this as
   the virtual one and use appropriate task/pid-searching functions.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: nuther build fix]
[akpm@linux-foundation.org: yet nuther build fix]
[akpm@linux-foundation.org: remove unneeded casts]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 13 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 98923882ba57..d809cdd6c0f1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -694,7 +694,7 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
                         q->info.si_signo = sig;
                         q->info.si_errno = 0;
                         q->info.si_code = SI_USER;
-                        q->info.si_pid = current->pid;
+                        q->info.si_pid = task_pid_vnr(current);
                         q->info.si_uid = current->uid;
                         break;
                 case (unsigned long) SEND_SIG_PRIV:
@@ -1089,7 +1089,7 @@ kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 {
         int error;
         rcu_read_lock();
-        error = kill_pid_info(sig, info, find_pid(pid));
+        error = kill_pid_info(sig, info, find_vpid(pid));
         rcu_read_unlock();
         return error;
 }
@@ -1160,9 +1160,9 @@ static int kill_something_info(int sig, struct siginfo *info, int pid)
                 read_unlock(&tasklist_lock);
                 ret = count ? retval : -ESRCH;
         } else if (pid < 0) {
-                ret = kill_pgrp_info(sig, info, find_pid(-pid));
+                ret = kill_pgrp_info(sig, info, find_vpid(-pid));
         } else {
-                ret = kill_pid_info(sig, info, find_pid(pid));
+                ret = kill_pid_info(sig, info, find_vpid(pid));
         }
         rcu_read_unlock();
         return ret;
@@ -1266,7 +1266,12 @@ EXPORT_SYMBOL(kill_pid);
 int
 kill_proc(pid_t pid, int sig, int priv)
 {
-        return kill_proc_info(sig, __si_special(priv), pid);
+        int ret;
+
+        rcu_read_lock();
+        ret = kill_pid_info(sig, __si_special(priv), find_pid(pid));
+        rcu_read_unlock();
+        return ret;
 }
 
 /*
@@ -1443,7 +1448,22 @@ void do_notify_parent(struct task_struct *tsk, int sig)
 
         info.si_signo = sig;
         info.si_errno = 0;
-        info.si_pid = tsk->pid;
+        /*
+         * we are under tasklist_lock here so our parent is tied to
+         * us and cannot exit and release its namespace.
+         *
+         * the only it can is to switch its nsproxy with sys_unshare,
+         * bu uncharing pid namespaces is not allowed, so we'll always
+         * see relevant namespace
+         *
+         * write_lock() currently calls preempt_disable() which is the
+         * same as rcu_read_lock(), but according to Oleg, this is not
+         * correct to rely on this
+         */
+        rcu_read_lock();
+        info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
+        rcu_read_unlock();
+
         info.si_uid = tsk->uid;
 
         /* FIXME: find out whether or not this is supposed to be c*time. */
@@ -1508,7 +1528,13 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
 
         info.si_signo = SIGCHLD;
         info.si_errno = 0;
-        info.si_pid = tsk->pid;
+        /*
+         * see comment in do_notify_parent() abot the following 3 lines
+         */
+        rcu_read_lock();
+        info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
+        rcu_read_unlock();
+
         info.si_uid = tsk->uid;
 
         /* FIXME: find out whether or not this is supposed to be c*time. */
@@ -1634,7 +1660,7 @@ void ptrace_notify(int exit_code)
         memset(&info, 0, sizeof info);
         info.si_signo = SIGTRAP;
         info.si_code = exit_code;
-        info.si_pid = current->pid;
+        info.si_pid = task_pid_vnr(current);
         info.si_uid = current->uid;
 
         /* Let the debugger run.  */
@@ -1804,7 +1830,7 @@ relock:
                                 info->si_signo = signr;
                                 info->si_errno = 0;
                                 info->si_code = SI_USER;
-                                info->si_pid = current->parent->pid;
+                                info->si_pid = task_pid_vnr(current->parent);
                                 info->si_uid = current->parent->uid;
                         }
 
@@ -2191,7 +2217,7 @@ sys_kill(int pid, int sig)
         info.si_signo = sig;
         info.si_errno = 0;
         info.si_code = SI_USER;
-        info.si_pid = current->tgid;
+        info.si_pid = task_tgid_vnr(current);
         info.si_uid = current->uid;
 
         return kill_something_info(sig, &info, pid);
@@ -2207,12 +2233,12 @@ static int do_tkill(int tgid, int pid, int sig)
         info.si_signo = sig;
         info.si_errno = 0;
         info.si_code = SI_TKILL;
-        info.si_pid = current->tgid;
+        info.si_pid = task_tgid_vnr(current);
         info.si_uid = current->uid;
 
         read_lock(&tasklist_lock);
-        p = find_task_by_pid(pid);
-        if (p && (tgid <= 0 || p->tgid == tgid)) {
+        p = find_task_by_pid_ns(pid, current->nsproxy->pid_ns);
+        if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
                 error = check_kill_permission(sig, &info, p);
                 /*
                  * The null signal is a permissions and process existence