Subject: [merged] kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch removed from -mm tree
To: oleg@xxxxxxxxxx,dserrg@xxxxxxxxx,ebiederm@xxxxxxxxxxxx,mhocko@xxxxxxx,xemul@xxxxxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 08 Jul 2013 12:36:09 -0700
The patch titled
Subject: kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists
has been removed from the -mm tree. Its filename was
kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists
copy_process() adds the new child to thread_group/init_task.tasks list and
then does attach_pid(child, PIDTYPE_PID). This means that the lockless
next_thread() or next_task() can see this thread with the wrong pid. Say,
"ls /proc/pid/task" can list the same inode twice.
We could move attach_pid(child, PIDTYPE_PID) up, but in this case
find_task_by_vpid() can find the new thread before it was fully
initialized.
And this is already true for PIDTYPE_PGID/PIDTYPE_SID, With this patch
copy_process() initializes child->pids[*].pid first, then calls
attach_pid() to insert the task into the pid->tasks list.
attach_pid() no longer need the "struct pid*" argument, it is always
called after pid_link->pid was already set.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Sergey Dyasly <dserrg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pid.h | 6 ++----
kernel/fork.c | 16 +++++++++++++---
kernel/pid.c | 12 ++++--------
3 files changed, 19 insertions(+), 15 deletions(-)
diff -puN include/linux/pid.h~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists include/linux/pid.h
--- a/include/linux/pid.h~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists
+++ a/include/linux/pid.h
@@ -86,11 +86,9 @@ extern struct task_struct *get_pid_task(
extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
/*
- * attach_pid() and detach_pid() must be called with the tasklist_lock
- * write-held.
+ * these helpers must be called with the tasklist_lock write-held.
*/
-extern void attach_pid(struct task_struct *task, enum pid_type type,
- struct pid *pid);
+extern void attach_pid(struct task_struct *task, enum pid_type);
extern void detach_pid(struct task_struct *task, enum pid_type);
extern void change_pid(struct task_struct *task, enum pid_type,
struct pid *pid);
diff -puN kernel/fork.c~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists kernel/fork.c
--- a/kernel/fork.c~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists
+++ a/kernel/fork.c
@@ -1121,6 +1121,12 @@ static void posix_cpu_timers_init(struct
INIT_LIST_HEAD(&tsk->cpu_timers[2]);
}
+static inline void
+init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
+{
+ task->pids[type].pid = pid;
+}
+
/*
* This creates a new process as a copy of the old one,
* but does not actually start it yet.
@@ -1449,7 +1455,11 @@ static struct task_struct *copy_process(
if (likely(p->pid)) {
ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
+ init_task_pid(p, PIDTYPE_PID, pid);
if (thread_group_leader(p)) {
+ init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
+ init_task_pid(p, PIDTYPE_SID, task_session(current));
+
if (is_child_reaper(pid)) {
ns_of_pid(pid)->child_reaper = p;
p->signal->flags |= SIGNAL_UNKILLABLE;
@@ -1457,10 +1467,10 @@ static struct task_struct *copy_process(
p->signal->leader_pid = pid;
p->signal->tty = tty_kref_get(current->signal->tty);
- attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
- attach_pid(p, PIDTYPE_SID, task_session(current));
list_add_tail(&p->sibling, &p->real_parent->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
+ attach_pid(p, PIDTYPE_PGID);
+ attach_pid(p, PIDTYPE_SID);
__this_cpu_inc(process_counts);
} else {
current->signal->nr_threads++;
@@ -1470,7 +1480,7 @@ static struct task_struct *copy_process(
list_add_tail_rcu(&p->thread_group,
&p->group_leader->thread_group);
}
- attach_pid(p, PIDTYPE_PID, pid);
+ attach_pid(p, PIDTYPE_PID);
nr_threads++;
}
diff -puN kernel/pid.c~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists kernel/pid.c
--- a/kernel/pid.c~kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists
+++ a/kernel/pid.c
@@ -373,14 +373,10 @@ EXPORT_SYMBOL_GPL(find_vpid);
/*
* attach_pid() must be called with the tasklist_lock write-held.
*/
-void attach_pid(struct task_struct *task, enum pid_type type,
- struct pid *pid)
+void attach_pid(struct task_struct *task, enum pid_type type)
{
- struct pid_link *link;
-
- link = &task->pids[type];
- link->pid = pid;
- hlist_add_head_rcu(&link->node, &pid->tasks[type]);
+ struct pid_link *link = &task->pids[type];
+ hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
}
static void __change_pid(struct task_struct *task, enum pid_type type,
@@ -412,7 +408,7 @@ void change_pid(struct task_struct *task
struct pid *pid)
{
__change_pid(task, type, pid);
- attach_pid(task, type, pid);
+ attach_pid(task, type);
}
/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
linux-next.patch
include-linux-schedh-dont-use-task-pid-tgid-in-same_thread_group-has_group_leader_pid.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
fput-task_work_add-can-fail-if-the-caller-has-passed-exit_task_work-fix.patch
fput-turn-list_head-delayed_fput_list-into-llist_head.patch
llist-fix-simplify-llist_add-and-llist_add_batch.patch
llist-llist_add-can-use-llist_add_batch.patch
vfree-dont-schedule-free_work-if-llist_add-returns-false.patch
autofs4-allow-autofs-to-work-outside-the-initial-pid-namespace.patch
autofs4-translate-pids-to-the-right-namespace-for-the-daemon.patch
ptrace-x86-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-powerpc-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-arm-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-sh-revert-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch
ptrace-revert-prepare-to-fix-racy-accesses-on-task-breakpoints.patch
ptrace-x86-simplify-the-disable-logic-in-ptrace_write_dr7.patch
ptrace-x86-dont-delay-disable-till-second-pass-in-ptrace_write_dr7.patch
ptrace-x86-introduce-ptrace_register_breakpoint.patch
ptrace-x86-ptrace_write_dr7-should-create-bp-if-disabled.patch
ptrace-x86-cleanup-ptrace_set_debugreg.patch
ptrace-ptrace_detach-should-do-flush_ptrace_hw_breakpointchild.patch
ptrace-x86-flush_ptrace_hw_breakpoint-shoule-clear-the-virtual-debug-registers.patch
signals-eventpoll-set-saved_sigmask-at-the-start.patch
move-exit_task_namespaces-outside-of-exit_notify-fix.patch
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