The patch titled
pids: de_thread: don't clear session/pgrp pids for the old leader
has been removed from the -mm tree. Its filename was
pids-de_thread-dont-clear-session-pgrp-pids-for-the-old-leader.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: pids: de_thread: don't clear session/pgrp pids for the old leader
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/pid.c | 1 -
1 file changed, 1 deletion(-)
diff -puN kernel/pid.c~pids-de_thread-dont-clear-session-pgrp-pids-for-the-old-leader kernel/pid.c
--- a/kernel/pid.c~pids-de_thread-dont-clear-session-pgrp-pids-for-the-old-leader
+++ a/kernel/pid.c
@@ -354,7 +354,6 @@ void transfer_pid(struct task_struct *ol
{
new->pids[type].pid = old->pids[type].pid;
hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
- old->pids[type].pid = NULL;
}
struct task_struct *pid_task(struct pid *pid, enum pid_type type)
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
posix-timers-bug-10460-discard-the-pending-signal-when-the-timer-is-destroyed.patch
workqueue-remove-redundant-function-invocation.patch
put_pid-make-sure-we-dont-free-the-live-pid.patch
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