From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch added to -mm tree Date: Tue, 11 Jun 2013 14:12:58 -0700 Message-ID: <51b792da.2iEzu5yjgTXFZu33%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43073 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756041Ab3FKVM7 (ORCPT ); Tue, 11 Jun 2013 17:12:59 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org, xemul@parallels.com, mhocko@suse.cz, ebiederm@xmission.com, dserrg@gmail.com, oleg@redhat.com Subject: + kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch added to -mm tree To: oleg@redhat.com,dserrg@gmail.com,ebiederm@xmission.com,mhocko@suse.cz,xemul@parallels.com From: akpm@linux-foundation.org Date: Tue, 11 Jun 2013 14:12:58 -0700 The patch titled Subject: kernel/fork.c:copy_process(): don't add the uninitialized child to thread/task/pid lists has been added to the -mm tree. Its filename is kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Oleg Nesterov 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 Cc: "Eric W. Biederman" Cc: Michal Hocko Cc: Pavel Emelyanov Cc: Sergey Dyasly Signed-off-by: Andrew Morton --- 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 @@ -1117,6 +1117,12 @@ 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. @@ -1445,7 +1451,11 @@ 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; @@ -1453,10 +1463,10 @@ 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++; @@ -1466,7 +1476,7 @@ 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@redhat.com are linux-next.patch audit-wait_for_auditd-should-use-task_uninterruptible.patch posix_cpu_timer-consolidate-expiry-time-type.patch posix_cpu_timers-consolidate-timer-list-cleanups.patch posix_cpu_timers-consolidate-expired-timers-check.patch posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule.patch posix_timers-fix-racy-timer-delta-caching-on-task-exit.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 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 x86-kill-tif_debug.patch ptrace-add-ability-to-get-set-signal-blocked-mask.patch usermodehelper-kill-the-sub_info-path-check.patch coredump-format_corename-can-leak-cn-corename.patch coredump-introduce-cn_vprintf.patch coredump-cn_vprintf-has-no-reason-to-call-vsnprintf-twice.patch coredump-kill-cn_escape-introduce-cn_esc_printf.patch coredump-kill-call_count-add-core_name_size.patch coredump-%-at-the-end-shouldnt-bypass-core_uses_pid-logic.patch coredump-%-at-the-end-shouldnt-bypass-core_uses_pid-logic-fix.patch fs-execc-de_thread-use-change_pid-rather-than-detach_pid-attach_pid.patch kernel-forkc-copy_process-unify-clone_thread-or-thread_group_leader-code.patch kernel-forkc-copy_process-dont-add-the-uninitialized-child-to-thread-task-pid-lists.patch kernel-forkc-copy_process-consolidate-the-lockless-clone_thread-checks.patch fs-execc-do_execve_common-use-current_user.patch wait-introduce-wait_event_commonwq-condition-state-timeout.patch wait-introduce-wait_event_commonwq-condition-state-timeout-checkpatch-fixes.patch wait-introduce-prepare_to_wait_event.patch wait-introduce-prepare_to_wait_event-checkpatch-fixes.patch