Re: [PATCH 7/16] Helpers to find the task by its numerical ids

sukadev
2007-07-10T04:00:56Z

Pavel Emelianov [xemul@openvz.org] wrote:
| When searching the task by numerical id on may need to find
| it using global pid (as it is done now in kernel) or by its
| virtual id, e.g. when sending a signal to a task from one
| namespace the sender will specify the task's virtual id.
|
| Signed-off-by: Pavel Emelianov <xemul@openvz.org>
|
| ---
|
| fs/proc/base.c | 2 +-
| include/linux/pid.h | 13 +++++++++++--
| include/linux/sched.h | 31 +++++++++++++++++++++++++++++--
| kernel/pid.c | 32 +++++++++++++++++---------------
| 4 files changed, 58 insertions(+), 20 deletions(-)
|
| --- ./fs/proc/base.c.ve6 2007-07-06 10:58:56.000000000 +0400
| +++ ./fs/proc/base.c 2007-07-06 11:03:41.000000000 +0400
| @@ -2230,7 +2230,7 @@ static struct task_struct *next_tgid(uns
| rcu_read_lock();
| retry:
| task = NULL;
| - pid = find_ge_pid(tgid);
| + pid = find_ge_pid(tgid, &init_pid_ns);
| if (pid) {
| tgid = pid->nr + 1;
| task = pid_task(pid, PIDTYPE_PID);
| --- ./include/linux/pid.h.ve6 2007-07-06 11:03:27.000000000 +0400
| +++ ./include/linux/pid.h 2007-07-06 11:03:27.000000000 +0400
| @@ -98,14 +98,23 @@ extern struct pid_namespace init_pid_ns;
| /*
| * look up a PID in the hash table. Must be called with the tasklist_lock
| * or rcu_read_lock() held.
| + *
| + * find_pid_ns() finds the pid in the namespace specified
| + * find_pid() find the pid by its global id, i.e. in the init namespace
| + * find_vpid() finr the pid by its virtual id, i.e. in the current namespace
| + *
| + * see also find_task_by_pid() set in include/linux/sched.h
| */
| -extern struct pid *FASTCALL(find_pid(int nr));
| +extern struct pid *FASTCALL(find_pid_ns(int nr, struct pid_namespace *ns));
| +
| +#define find_vpid(pid) find_pid_ns(pid, current->nsproxy->pid_ns)
| +#define find_pid(pid) find_pid_ns(pid, &init_pid_ns)

Adding a second interface maybe more confusing to drivers and non-pid
users.

But more importantly, modifying find_pid() to refer to only init_pid_ns
would require auditing existing find_pid() callers and switching them to
find_vpid().

For instance if capset() is called from a child pid namespace, the 'pid'
would refer to the pid or pgid from child pid ns. But cap_set_pg() calls
find_pid() which gets the number from init_pid_ns.

Is there a similar issue with sunos_killpg() ?