Quoting Serge E. Hallyn ([EMAIL PROTECTED]):
> >From 945fe66259cd0cfdc2fe846287b7821e329a558c Mon Sep 17 00:00:00 2001
> From: [EMAIL PROTECTED] <[EMAIL PROTECTED](none)>
> Date: Tue, 9 Oct 2007 08:30:30 -0700
> Subject: [PATCH] namespaces: introduce sys_hijack (v4)
>
> Move most of do_fork() into a new do_fork_task() which acts on
> a new argument, task, rather than on current. do_fork() becomes
> a call to do_fork_task(current, ...).
>
> Introduce sys_hijack (for x86 only so far). It is like clone, but
> in place of a stack pointer (which is assumed null) it accepts a
> pid. The process identified by that pid is the one which is
> actually cloned. Some state - include the file table, the signals
> and sighand (and hence tty), and the ->parent are taken from the
> calling process.
>
> The effect is a sort of namespace enter. The following program
> uses sys_hijack to 'enter' all namespaces of the specified pid.
> For instance in one terminal, do
>
> mount -t cgroup -ons /cgroup
> hostname
> qemu
> ns_exec -u /bin/sh
> hostname serge
> echo $$
> 1073
> cat /proc/$$/cgroup
> ns:/node_1073
>
> In another terminal then do
>
> hostname
> qemu
> cat /proc/$$/cgroup
> ns:/
> hijack 1073
> hostname
> serge
> cat /proc/$$/cgroup
> ns:/node_1073
>
> sys_hijack is arch-dependent and is only implemented for i386 so far.
>
> Changelog:
> Aug 23: send a stop signal to the hijacked process
> (like ptrace does).
> Oct 09: Update for 2.6.23-rc8-mm2 (mainly pidns)
> Don't take task_lock under rcu_read_lock
> Send hijacked process to cgroup_fork() as
> the first argument.
> Removed some unneeded task_locks.
Thanks to Cedric for finding an oops when using pid namespaces. The
following patch fixes the problem.
In addition, to hijack a process in another pid namespace, the
hijack.c test program needs to be updated to do waitpid as
while(waitpid(-1, &status, __WALL) != -1)
;
as shown below:
==============================================================
hijack.c
==============================================================
int do_clone_task(void)
{
execl("/bin/sh", "/bin/sh", NULL);
}
int main(int argc, char *argv[])
{
int pid;
int ret;
int status;
if (argc < 2)
return 1;
pid = atoi(argv[1]);
ret = syscall(327, SIGCHLD, pid, NULL, NULL);
if (ret == 0) {
return do_clone_task();
} else if (ret < 0) {
perror("sys_hijack");
} else {
printf("waiting on cloned process %d\n", ret);
while(waitpid(-1, &status, __WALL) != -1)
;
printf("cloned process %d exited with %d\n", ret, status);
}
return ret;
}
==============================================================
>From f1d9621e8325471e3ccde7f5fc2ed5a7be582524 Mon Sep 17 00:00:00 2001
From: [EMAIL PROTECTED] <[EMAIL PROTECTED](none)>
Date: Thu, 11 Oct 2007 14:26:05 -0700
Subject: [PATCH 2/2] hijack: pidns bugfix
My change to alloc_pid was bogus and introduced a pidns bug. Fix.
Signed-off-by: [EMAIL PROTECTED] <[EMAIL PROTECTED](none)>
---
include/linux/pid.h | 2 +-
kernel/fork.c | 2 +-
kernel/pid.c | 5 ++---
3 files changed, 4 insertions(+), 5 deletions(-)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 145dce7..e29a900 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -119,7 +119,7 @@ extern struct pid *find_pid(int nr);
extern struct pid *find_get_pid(int nr);
extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
-extern struct pid *alloc_pid(struct task_struct *task);
+extern struct pid *alloc_pid(struct pid_namespace *ns);
extern void FASTCALL(free_pid(struct pid *pid));
extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);
diff --git a/kernel/fork.c b/kernel/fork.c
index ac73f3e..c1d4672 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1154,7 +1154,7 @@ static struct task_struct *copy_process(struct
task_struct *task,
if (pid != &init_struct_pid) {
retval = -ENOMEM;
- pid = alloc_pid(task);
+ pid = alloc_pid(task_active_pid_ns(p));
if (!pid)
goto bad_fork_cleanup_namespaces;
diff --git a/kernel/pid.c b/kernel/pid.c
index b887a6a..d7388d7 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -238,15 +238,14 @@ fastcall void free_pid(struct pid *pid)
call_rcu(&pid->rcu, delayed_put_pid);
}
-struct pid *alloc_pid(struct task_struct *srctsk)
+struct pid *alloc_pid(struct pid_namespace *ns)
{
struct pid *pid;
enum pid_type type;
int i, nr;
- struct pid_namespace *tmp, *ns;
+ struct pid_namespace *tmp;
struct upid *upid;
- ns = task_active_pid_ns(srctsk);
pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
if (!pid)
goto out;
--
1.5.1
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