linux-kernel - Re: Process id recycling and status of tasks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 23 Oct 2009 10:13:24 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	"Leonidas ." <leonidas137@...il.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Process id recycling and status of tasks

Leonidas . wrote:
> 1. What would be an ideal way to check if a task is alive or dead from
> kernel space?

Get a reference to the task's pid (call get_task_pid(), or get_pid() on
the return value of task_pid()), then later check whether pid_task()
works.

(pid_alive() is not what you want because this would require that you
hold a reference to the task_struct.)

> even though a certain pid might exist, it might have got recycled by
> the time I check again, right?

The functions above do not work with PID numbers but with struct pid
which is a reference-counted object.  (The functions with "get" in their
name increase the reference count, so don't forget to put_pid() when you
no longer need it.)  See also the big comment in include/linux/pid.h.

HTH
Clemens
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/