The patch titled pids: introduce change_pid() helper has been added to the -mm tree. Its filename is pids-introduce-change_pid-helper.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 *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: pids: introduce change_pid() helper From: Oleg Nesterov <oleg@xxxxxxxxxx> Based on Eric W. Biederman's idea. Without tasklist_lock held task_session()/task_pgrp() can return NULL if the caller races with setprgp()/setsid() which does detach_pid() + attach_pid(). This can happen even if task == current. Intoduce the new helper, change_pid(), which should be used instead. This way the caller always sees the special pid != NULL, either old or new. Also change the prototype of attach_pid(), it always returns 0 and nobody check the returned value. 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> --- include/linux/pid.h | 6 ++++-- kernel/pid.c | 21 ++++++++++++++++----- 2 files changed, 20 insertions(+), 7 deletions(-) diff -puN include/linux/pid.h~pids-introduce-change_pid-helper include/linux/pid.h --- a/include/linux/pid.h~pids-introduce-change_pid-helper +++ a/include/linux/pid.h @@ -89,9 +89,11 @@ extern struct pid *get_task_pid(struct t * attach_pid() and detach_pid() must be called with the tasklist_lock * write-held. */ -extern int attach_pid(struct task_struct *task, enum pid_type type, - struct pid *pid); +extern void attach_pid(struct task_struct *task, enum pid_type type, + struct pid *pid); 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); extern void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type); diff -puN kernel/pid.c~pids-introduce-change_pid-helper kernel/pid.c --- a/kernel/pid.c~pids-introduce-change_pid-helper +++ a/kernel/pid.c @@ -318,7 +318,7 @@ EXPORT_SYMBOL_GPL(find_pid); /* * attach_pid() must be called with the tasklist_lock write-held. */ -int attach_pid(struct task_struct *task, enum pid_type type, +void attach_pid(struct task_struct *task, enum pid_type type, struct pid *pid) { struct pid_link *link; @@ -326,11 +326,10 @@ int attach_pid(struct task_struct *task, link = &task->pids[type]; link->pid = pid; hlist_add_head_rcu(&link->node, &pid->tasks[type]); - - return 0; } -void detach_pid(struct task_struct *task, enum pid_type type) +static void __change_pid(struct task_struct *task, enum pid_type type, + struct pid *new) { struct pid_link *link; struct pid *pid; @@ -340,7 +339,7 @@ void detach_pid(struct task_struct *task pid = link->pid; hlist_del_rcu(&link->node); - link->pid = NULL; + link->pid = new; for (tmp = PIDTYPE_MAX; --tmp >= 0; ) if (!hlist_empty(&pid->tasks[tmp])) @@ -349,6 +348,18 @@ void detach_pid(struct task_struct *task free_pid(pid); } +void detach_pid(struct task_struct *task, enum pid_type type) +{ + __change_pid(task, type, NULL); +} + +void change_pid(struct task_struct *task, enum pid_type type, + struct pid *pid) +{ + __change_pid(task, type, pid); + attach_pid(task, type, pid); +} + /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type type) _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch x86-handle_vm86_trap-cleanup.patch git-hrt.patch bsd_acct-plain-current-real_parent-access-is-not-always-safe.patch bsd_acct-using-task_struct-tgid-is-not-right-in-pid-namespaces.patch mmap_region-cleanup-the-final-vma_merge-related-code.patch kthread-call-wake_up_process-without-the-lock-being-held.patch remove-unused-variable-from-send_signal.patch turn-legacy_queue-macro-into-static-inline-function.patch consolidate-checking-for-ignored-legacy-signals.patch consolidate-checking-for-ignored-legacy-signals-simplify.patch signals-do_signal_stop-use-signal_group_exit.patch signals-do_group_exit-use-signal_group_exit-more-consistently.patch lock_task_sighand-add-rcu-lock-unlock.patch k_getrusage-dont-take-rcu_read_lock.patch do_task_stat-dont-take-rcu_read_lock.patch signals-consolidate-checks-for-whether-or-not-to-ignore-a-signal.patch signals-clean-dequeue_signal-from-excess-checks-and-assignments.patch signals-consolidate-send_sigqueue-and-send_group_sigqueue.patch signals-cleanup-security_task_kill-usage-implementation.patch signals-re-assign-cld_continued-notification-from-the-sender-to-reciever.patch kill_pid_info-dont-take-now-unneeded-tasklist_lock.patch handle_stop_signal-unify-partial-full-stop-handling.patch handle_stop_signal-use-the-cached-p-signal-value.patch get_signal_to_deliver-use-the-cached-signal-sighand-values.patch signals-send_sigqueue-dont-take-rcu-lock.patch signals-send_sigqueue-dont-forget-about-handle_stop_signal.patch signals-__group_complete_signal-cache-the-value-of-p-signal.patch signals-send_group_sigqueue-dont-take-tasklist_lock.patch signals-move-handle_stop_signal-into-send_signal.patch signals-do_tkill-dont-use-tasklist_lock.patch signals-do_tkill-dont-use-tasklist_lock-comment.patch signals-send_sig_info-dont-take-tasklist_lock.patch signals-microoptimize-the-usage-of-curr_target.patch signals-move-the-definition-of-__group_complete_signal-up.patch signals-change-send_signal-do_send_sigqueue-to-take-boolean-group-parameter.patch signals-use-__group_complete_signal-for-the-specific-signals-too.patch signals-fold-complete_signal-into-send_signal-do_send_sigqueue.patch signals-unify-send_sigqueue-send_group_sigqueue-completely.patch signals-join-send_sigqueue-with-send_group_sigqueue.patch signals-handle_stop_signal-dont-worry-about-sigkill.patch signals-cleanup-the-usage-of-print_fatal_signal.patch signals-fold-sig_ignored-into-handle_stop_signal.patch signals-fold-sig_ignored-into-handle_stop_signal-comment.patch signals-document-cld_continued-notification-mechanics.patch signals-document-cld_continued-notification-mechanics-more.patch signals-send_signal-be-paranoid-about-signalfd_notify.patch signals-check_kill_permission-check-session-under-tasklist_lock.patch ptrace-introduce-task_detached-helper.patch reparent_thread-use-same_thread_group.patch document-de_thread-with-exit_notify-connection.patch ptrace-introduce-ptrace_reparented-helper.patch ptrace-__ptrace_unlink-use-the-ptrace_reparented-helper.patch ptrace-ptrace_attach-use-send_sig_info-instead-force_sig_specific.patch workqueues-shrink-cpu_populated_map-when-cpu-dies.patch workqueues-shrink-cpu_populated_map-when-cpu-dies-fix.patch cleanup_workqueue_thread-remove-the-unneeded-cpu-parameter.patch simplify-cpu_hotplug_begin-put_online_cpus.patch redo-locking-of-tty-pgrp.patch resume-tty-on-susp-and-fix-crnl-order-in-n_tty-line-discipline.patch tty_io-fix-remaining-pid-struct-locking.patch tty_io-fix-remaining-pid-struct-locking-small-cleanup.patch procfs-task-exe-symlink.patch procfs-task-exe-symlink-fix.patch procfs-task-exe-symlink-fix-2.patch free_pidmap-turn-it-into-free_pidmapstruct-upid.patch pids-de_thread-dont-clear-session-pgrp-pids-for-the-old-leader.patch pids-introduce-change_pid-helper.patch pids-sys_setpgid-use-change_pid-helper.patch pids-__set_special_pids-use-change_pid-helper.patch put_pid-make-sure-we-dont-free-the-live-pid.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html