Commit e46bc9b6 authored by Oleg Nesterov's avatar Oleg Nesterov

Merge branch 'ptrace' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into ptrace

parents 2b9accbe 321fb561
......@@ -1659,6 +1659,7 @@ static int zap_process(struct task_struct *start, int exit_code)
t = start;
do {
task_clear_group_stop_pending(t);
if (t != current && t->mm) {
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
......
......@@ -653,9 +653,8 @@ struct signal_struct {
* Bits in flags field of signal_struct.
*/
#define SIGNAL_STOP_STOPPED 0x00000001 /* job control stop in effect */
#define SIGNAL_STOP_DEQUEUED 0x00000002 /* stop signal dequeued */
#define SIGNAL_STOP_CONTINUED 0x00000004 /* SIGCONT since WCONTINUED reap */
#define SIGNAL_GROUP_EXIT 0x00000008 /* group exit in progress */
#define SIGNAL_STOP_CONTINUED 0x00000002 /* SIGCONT since WCONTINUED reap */
#define SIGNAL_GROUP_EXIT 0x00000004 /* group exit in progress */
/*
* Pending notifications to parent.
*/
......@@ -1261,6 +1260,7 @@ struct task_struct {
int exit_state;
int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies */
unsigned int group_stop; /* GROUP_STOP_*, siglock protected */
/* ??? */
unsigned int personality;
unsigned did_exec:1;
......@@ -1777,6 +1777,17 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define tsk_used_math(p) ((p)->flags & PF_USED_MATH)
#define used_math() tsk_used_math(current)
/*
* task->group_stop flags
*/
#define GROUP_STOP_SIGMASK 0xffff /* signr of the last group stop */
#define GROUP_STOP_PENDING (1 << 16) /* task should stop for group stop */
#define GROUP_STOP_CONSUME (1 << 17) /* consume group stop count */
#define GROUP_STOP_TRAPPING (1 << 18) /* switching from STOPPED to TRACED */
#define GROUP_STOP_DEQUEUED (1 << 19) /* stop signal dequeued */
extern void task_clear_group_stop_pending(struct task_struct *task);
#ifdef CONFIG_PREEMPT_RCU
#define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */
......
......@@ -468,33 +468,6 @@ static inline int tracehook_get_signal(struct task_struct *task,
return 0;
}
/**
* tracehook_notify_jctl - report about job control stop/continue
* @notify: zero, %CLD_STOPPED or %CLD_CONTINUED
* @why: %CLD_STOPPED or %CLD_CONTINUED
*
* This is called when we might call do_notify_parent_cldstop().
*
* @notify is zero if we would not ordinarily send a %SIGCHLD,
* or is the %CLD_STOPPED or %CLD_CONTINUED .si_code for %SIGCHLD.
*
* @why is %CLD_STOPPED when about to stop for job control;
* we are already in %TASK_STOPPED state, about to call schedule().
* It might also be that we have just exited (check %PF_EXITING),
* but need to report that a group-wide stop is complete.
*
* @why is %CLD_CONTINUED when waking up after job control stop and
* ready to make a delayed @notify report.
*
* Return the %CLD_* value for %SIGCHLD, or zero to generate no signal.
*
* Called with the siglock held.
*/
static inline int tracehook_notify_jctl(int notify, int why)
{
return notify ?: (current->ptrace & PT_PTRACED) ? why : 0;
}
/**
* tracehook_finish_jctl - report about return from job control stop
*
......
......@@ -1538,33 +1538,83 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
return 0;
}
if (likely(!ptrace) && unlikely(task_ptrace(p))) {
/* dead body doesn't have much to contribute */
if (p->exit_state == EXIT_DEAD)
return 0;
/* slay zombie? */
if (p->exit_state == EXIT_ZOMBIE) {
/*
* This child is hidden by ptrace.
* We aren't allowed to see it now, but eventually we will.
* A zombie ptracee is only visible to its ptracer.
* Notification and reaping will be cascaded to the real
* parent when the ptracer detaches.
*/
if (likely(!ptrace) && unlikely(task_ptrace(p))) {
/* it will become visible, clear notask_error */
wo->notask_error = 0;
return 0;
}
if (p->exit_state == EXIT_DEAD)
return 0;
/* we don't reap group leaders with subthreads */
if (!delay_group_leader(p))
return wait_task_zombie(wo, p);
/*
* We don't reap group leaders with subthreads.
* Allow access to stopped/continued state via zombie by
* falling through. Clearing of notask_error is complex.
*
* When !@ptrace:
*
* If WEXITED is set, notask_error should naturally be
* cleared. If not, subset of WSTOPPED|WCONTINUED is set,
* so, if there are live subthreads, there are events to
* wait for. If all subthreads are dead, it's still safe
* to clear - this function will be called again in finite
* amount time once all the subthreads are released and
* will then return without clearing.
*
* When @ptrace:
*
* Stopped state is per-task and thus can't change once the
* target task dies. Only continued and exited can happen.
* Clear notask_error if WCONTINUED | WEXITED.
*/
if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
wo->notask_error = 0;
} else {
/*
* If @p is ptraced by a task in its real parent's group,
* hide group stop/continued state when looking at @p as
* the real parent; otherwise, a single stop can be
* reported twice as group and ptrace stops.
*
* If a ptracer wants to distinguish the two events for its
* own children, it should create a separate process which
* takes the role of real parent.
*/
if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
return wait_task_zombie(wo, p);
if (likely(!ptrace) && task_ptrace(p) &&
same_thread_group(p->parent, p->real_parent))
return 0;
/*
* It's stopped or running now, so it might
* later continue, exit, or stop again.
* @p is alive and it's gonna stop, continue or exit, so
* there always is something to wait for.
*/
wo->notask_error = 0;
}
/*
* Wait for stopped. Depending on @ptrace, different stopped state
* is used and the two don't interact with each other.
*/
if (task_stopped_code(p, ptrace))
return wait_task_stopped(wo, ptrace, p);
/*
* Wait for continued. There's only one continued state and the
* ptracer can consume it which can confuse the real parent. Don't
* use WCONTINUED from ptracer. You don't need or want it.
*/
return wait_task_continued(wo, p);
}
......
......@@ -37,35 +37,33 @@ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
child->parent = new_parent;
}
/*
* Turn a tracing stop into a normal stop now, since with no tracer there
* would be no way to wake it up with SIGCONT or SIGKILL. If there was a
* signal sent that would resume the child, but didn't because it was in
* TASK_TRACED, resume it now.
* Requires that irqs be disabled.
*/
static void ptrace_untrace(struct task_struct *child)
{
spin_lock(&child->sighand->siglock);
if (task_is_traced(child)) {
/*
* If the group stop is completed or in progress,
* this thread was already counted as stopped.
*/
if (child->signal->flags & SIGNAL_STOP_STOPPED ||
child->signal->group_stop_count)
__set_task_state(child, TASK_STOPPED);
else
signal_wake_up(child, 1);
}
spin_unlock(&child->sighand->siglock);
}
/*
* unptrace a task: move it back to its original parent and
* remove it from the ptrace list.
/**
* __ptrace_unlink - unlink ptracee and restore its execution state
* @child: ptracee to be unlinked
*
* Must be called with the tasklist lock write-held.
* Remove @child from the ptrace list, move it back to the original parent,
* and restore the execution state so that it conforms to the group stop
* state.
*
* Unlinking can happen via two paths - explicit PTRACE_DETACH or ptracer
* exiting. For PTRACE_DETACH, unless the ptracee has been killed between
* ptrace_check_attach() and here, it's guaranteed to be in TASK_TRACED.
* If the ptracer is exiting, the ptracee can be in any state.
*
* After detach, the ptracee should be in a state which conforms to the
* group stop. If the group is stopped or in the process of stopping, the
* ptracee should be put into TASK_STOPPED; otherwise, it should be woken
* up from TASK_TRACED.
*
* If the ptracee is in TASK_TRACED and needs to be moved to TASK_STOPPED,
* it goes through TRACED -> RUNNING -> STOPPED transition which is similar
* to but in the opposite direction of what happens while attaching to a
* stopped task. However, in this direction, the intermediate RUNNING
* state is not hidden even from the current ptracer and if it immediately
* re-attaches and performs a WNOHANG wait(2), it may fail.
*
* CONTEXT:
* write_lock_irq(tasklist_lock)
*/
void __ptrace_unlink(struct task_struct *child)
{
......@@ -75,8 +73,27 @@ void __ptrace_unlink(struct task_struct *child)
child->parent = child->real_parent;
list_del_init(&child->ptrace_entry);
if (task_is_traced(child))
ptrace_untrace(child);
spin_lock(&child->sighand->siglock);
/*
* Reinstate GROUP_STOP_PENDING if group stop is in effect and
* @child isn't dead.
*/
if (!(child->flags & PF_EXITING) &&
(child->signal->flags & SIGNAL_STOP_STOPPED ||
child->signal->group_stop_count))
child->group_stop |= GROUP_STOP_PENDING;
/*
* If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
* @child in the butt. Note that @resume should be used iff @child
* is in TASK_TRACED; otherwise, we might unduly disrupt
* TASK_KILLABLE sleeps.
*/
if (child->group_stop & GROUP_STOP_PENDING || task_is_traced(child))
signal_wake_up(child, task_is_traced(child));
spin_unlock(&child->sighand->siglock);
}
/*
......@@ -95,16 +112,14 @@ int ptrace_check_attach(struct task_struct *child, int kill)
*/
read_lock(&tasklist_lock);
if ((child->ptrace & PT_PTRACED) && child->parent == current) {
ret = 0;
/*
* child->sighand can't be NULL, release_task()
* does ptrace_unlink() before __exit_signal().
*/
spin_lock_irq(&child->sighand->siglock);
if (task_is_stopped(child))
child->state = TASK_TRACED;
else if (!task_is_traced(child) && !kill)
ret = -ESRCH;
WARN_ON_ONCE(task_is_stopped(child));
if (task_is_traced(child) || kill)
ret = 0;
spin_unlock_irq(&child->sighand->siglock);
}
read_unlock(&tasklist_lock);
......@@ -168,6 +183,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
static int ptrace_attach(struct task_struct *task)
{
bool wait_trap = false;
int retval;
audit_ptrace(task);
......@@ -207,12 +223,42 @@ static int ptrace_attach(struct task_struct *task)
__ptrace_link(task, current);
send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
spin_lock(&task->sighand->siglock);
/*
* If the task is already STOPPED, set GROUP_STOP_PENDING and
* TRAPPING, and kick it so that it transits to TRACED. TRAPPING
* will be cleared if the child completes the transition or any
* event which clears the group stop states happens. We'll wait
* for the transition to complete before returning from this
* function.
*
* This hides STOPPED -> RUNNING -> TRACED transition from the
* attaching thread but a different thread in the same group can
* still observe the transient RUNNING state. IOW, if another
* thread's WNOHANG wait(2) on the stopped tracee races against
* ATTACH, the wait(2) may fail due to the transient RUNNING.
*
* The following task_is_stopped() test is safe as both transitions
* in and out of STOPPED are protected by siglock.
*/
if (task_is_stopped(task)) {
task->group_stop |= GROUP_STOP_PENDING | GROUP_STOP_TRAPPING;
signal_wake_up(task, 1);
wait_trap = true;
}
spin_unlock(&task->sighand->siglock);
retval = 0;
unlock_tasklist:
write_unlock_irq(&tasklist_lock);
unlock_creds:
mutex_unlock(&task->signal->cred_guard_mutex);
out:
if (wait_trap)
wait_event(current->signal->wait_chldexit,
!(task->group_stop & GROUP_STOP_TRAPPING));
return retval;
}
......@@ -315,8 +361,6 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
if (child->ptrace) {
child->exit_code = data;
dead = __ptrace_detach(current, child);
if (!child->exit_state)
wake_up_state(child, TASK_TRACED | TASK_STOPPED);
}
write_unlock_irq(&tasklist_lock);
......
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