diff options
author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-04-30 00:54:25 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-30 08:29:48 -0700 |
commit | 65450cebc6a2efde80ed45514f727e6e4dc1eafd (patch) | |
tree | 26d3cdb75b4e94eed773c71c4bcb3c5d5843eed3 /include/linux/root_dev.h | |
parent | 5cd204550b1a006f2b0c986b0e0f53220ebfd391 (diff) |
pids: de_thread: don't clear session/pgrp pids for the old leader
Based on Eric W. Biederman's idea.
Unless task == current, without tasklist_lock held task_session()/task_pgrp()
can return NULL if the caller races with de_thread() which switches the group
leader.
Change transfer_pid() to not clear old->pids[type].pid for the old leader.
This means that its .pid can point to "nowhere", but this is already true for
sub-threads, and the old leader is not group_leader() any longer. IOW, with
or without this change we can't trust task's special pids unless it is the
group leader.
With this change the following code
rcu_read_lock();
task = find_task_by_xxx();
do_something(task_pgrp(task), task_session(task));
rcu_read_unlock();
can't race with exec and hit the NULL pid.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/root_dev.h')
0 files changed, 0 insertions, 0 deletions