From: Oleg Nesterov <oleg@redhat.com>
Date: Thu, 2 Apr 2009 23:58:35 +0000 (-0700)
Subject: pids: document task_pgrp/task_session is not safe without tasklist/rcu
X-Git-Tag: v2.6.30-rc1~312
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6dda81f4384b94930826eded254d8c16f89a9248;p=pandora-kernel.git

pids: document task_pgrp/task_session is not safe without tasklist/rcu

Even if task == current, it is not safe to dereference the result of
task_pgrp/task_session.  We can race with another thread which changes the
special pid via setpgid/setsid.

Document this.  The next 2 patches give an example of the unsafe usage, we
have more bad users.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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