forget_original_parent: split out the un-ptrace part
By discussion with Roland.
- Rename ptrace_exit() to exit_ptrace(), and change it to do all the
necessary work with ->ptraced list by its own.
- Move this code from exit.c to ptrace.c
- Update the comment in ptrace_detach() to explain the rechecking of
the child->ptrace.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 1a2b0cb..67c1565 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -94,7 +94,7 @@
extern void __ptrace_link(struct task_struct *child,
struct task_struct *new_parent);
extern void __ptrace_unlink(struct task_struct *child);
-extern int __ptrace_detach(struct task_struct *tracer, struct task_struct *p);
+extern void exit_ptrace(struct task_struct *tracer);
extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);
#define PTRACE_MODE_READ 1
#define PTRACE_MODE_ATTACH 2
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9186f8c..b47c94e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2061,6 +2061,11 @@
#define delay_group_leader(p) \
(thread_group_leader(p) && !thread_group_empty(p))
+static inline int task_detached(struct task_struct *p)
+{
+ return p->exit_signal == -1;
+}
+
/*
* Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
* subscriptions and synchronises with wait4(). Also used in procfs. Also
diff --git a/kernel/exit.c b/kernel/exit.c
index 3e09b7c..506693d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -61,11 +61,6 @@
static void exit_mm(struct task_struct * tsk);
-static inline int task_detached(struct task_struct *p)
-{
- return p->exit_signal == -1;
-}
-
static void __unhash_process(struct task_struct *p)
{
nr_threads--;
@@ -731,85 +726,6 @@
mmput(mm);
}
-/*
- * Called with irqs disabled, returns true if childs should reap themselves.
- */
-static int ignoring_children(struct sighand_struct *sigh)
-{
- int ret;
- spin_lock(&sigh->siglock);
- ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
- (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
- spin_unlock(&sigh->siglock);
- return ret;
-}
-
-/* Returns nonzero if the tracee should be released. */
-int __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
-{
- __ptrace_unlink(p);
-
- if (p->exit_state != EXIT_ZOMBIE)
- return 0;
- /*
- * If it's a zombie, our attachedness prevented normal
- * parent notification or self-reaping. Do notification
- * now if it would have happened earlier. If it should
- * reap itself we return true.
- *
- * If it's our own child, there is no notification to do.
- * But if our normal children self-reap, then this child
- * was prevented by ptrace and we must reap it now.
- */
- if (!task_detached(p) && thread_group_empty(p)) {
- if (!same_thread_group(p->real_parent, tracer))
- do_notify_parent(p, p->exit_signal);
- else if (ignoring_children(tracer->sighand))
- p->exit_signal = -1;
- }
-
- if (!task_detached(p))
- return 0;
-
- /* Mark it as in the process of being reaped. */
- p->exit_state = EXIT_DEAD;
- return 1;
-}
-
-/*
- * Detach all tasks we were using ptrace on.
- * Any that need to be release_task'd are put on the @dead list.
- *
- * Called with write_lock(&tasklist_lock) held.
- */
-static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
-{
- struct task_struct *p, *n;
-
- list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
- if (__ptrace_detach(parent, p))
- list_add(&p->ptrace_entry, dead);
- }
-}
-
-/*
- * Finish up exit-time ptrace cleanup.
- *
- * Called without locks.
- */
-static void ptrace_exit_finish(struct task_struct *parent,
- struct list_head *dead)
-{
- struct task_struct *p, *n;
-
- BUG_ON(!list_empty(&parent->ptraced));
-
- list_for_each_entry_safe(p, n, dead, ptrace_entry) {
- list_del_init(&p->ptrace_entry);
- release_task(p);
- }
-}
-
/* Returns nonzero if the child should be released. */
static int reparent_thread(struct task_struct *p, struct task_struct *father)
{
@@ -894,12 +810,10 @@
struct task_struct *p, *n, *reaper;
LIST_HEAD(ptrace_dead);
+ exit_ptrace(father);
+
write_lock_irq(&tasklist_lock);
reaper = find_new_reaper(father);
- /*
- * First clean up ptrace if we were using it.
- */
- ptrace_exit(father, &ptrace_dead);
list_for_each_entry_safe(p, n, &father->children, sibling) {
p->real_parent = reaper;
@@ -914,7 +828,10 @@
write_unlock_irq(&tasklist_lock);
BUG_ON(!list_empty(&father->children));
- ptrace_exit_finish(father, &ptrace_dead);
+ list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
+ list_del_init(&p->ptrace_entry);
+ release_task(p);
+ }
}
/*
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index ee553b6..f5a9fa5 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -235,9 +235,57 @@
return retval;
}
+/*
+ * Called with irqs disabled, returns true if childs should reap themselves.
+ */
+static int ignoring_children(struct sighand_struct *sigh)
+{
+ int ret;
+ spin_lock(&sigh->siglock);
+ ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
+ (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
+ spin_unlock(&sigh->siglock);
+ return ret;
+}
+
+/*
+ * Called with tasklist_lock held for writing.
+ * Unlink a traced task, and clean it up if it was a traced zombie.
+ * Return true if it needs to be reaped with release_task().
+ * (We can't call release_task() here because we already hold tasklist_lock.)
+ *
+ * If it's a zombie, our attachedness prevented normal parent notification
+ * or self-reaping. Do notification now if it would have happened earlier.
+ * If it should reap itself, return true.
+ *
+ * If it's our own child, there is no notification to do.
+ * But if our normal children self-reap, then this child
+ * was prevented by ptrace and we must reap it now.
+ */
+static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
+{
+ __ptrace_unlink(p);
+
+ if (p->exit_state == EXIT_ZOMBIE) {
+ if (!task_detached(p) && thread_group_empty(p)) {
+ if (!same_thread_group(p->real_parent, tracer))
+ do_notify_parent(p, p->exit_signal);
+ else if (ignoring_children(tracer->sighand))
+ p->exit_signal = -1;
+ }
+ if (task_detached(p)) {
+ /* Mark it as in the process of being reaped. */
+ p->exit_state = EXIT_DEAD;
+ return true;
+ }
+ }
+
+ return false;
+}
+
int ptrace_detach(struct task_struct *child, unsigned int data)
{
- int dead = 0;
+ bool dead = false;
if (!valid_signal(data))
return -EIO;
@@ -247,7 +295,10 @@
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
write_lock_irq(&tasklist_lock);
- /* protect against de_thread()->release_task() */
+ /*
+ * This child can be already killed. Make sure de_thread() or
+ * our sub-thread doing do_wait() didn't do release_task() yet.
+ */
if (child->ptrace) {
child->exit_code = data;
@@ -264,6 +315,29 @@
return 0;
}
+/*
+ * Detach all tasks we were using ptrace on.
+ */
+void exit_ptrace(struct task_struct *tracer)
+{
+ struct task_struct *p, *n;
+ LIST_HEAD(ptrace_dead);
+
+ write_lock_irq(&tasklist_lock);
+ list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
+ if (__ptrace_detach(tracer, p))
+ list_add(&p->ptrace_entry, &ptrace_dead);
+ }
+ write_unlock_irq(&tasklist_lock);
+
+ BUG_ON(!list_empty(&tracer->ptraced));
+
+ list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
+ list_del_init(&p->ptrace_entry);
+ release_task(p);
+ }
+}
+
int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
{
int copied = 0;
