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forget_original_parent: split out the un-ptrace part

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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>
This commit is contained in:
Oleg Nesterov 2009-04-02 16:58:18 -07:00 committed by Linus Torvalds
parent 7f5d3652d4
commit 39c626ae47
4 changed files with 88 additions and 92 deletions
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2
include/linux/ptrace.h
View File

@ -94,7 +94,7 @@ extern void ptrace_notify(int exit_code);
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

5
include/linux/sched.h
View File

@ -2061,6 +2061,11 @@ static inline int thread_group_empty(struct task_struct *p)
#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

95
kernel/exit.c
View File

@ -61,11 +61,6 @@ DEFINE_TRACE(sched_process_wait);
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 @@ static void exit_mm(struct task_struct * tsk)
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 @@ static void forget_original_parent(struct task_struct *father)
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 @@ static void forget_original_parent(struct task_struct *father)
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);
}
}
/*

78
kernel/ptrace.c
View File

@ -235,9 +235,57 @@ int ptrace_attach(struct task_struct *task)
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 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
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 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
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;