diff options
| -rw-r--r-- | kernel/ptrace.c | 59 |
1 files changed, 39 insertions, 20 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index e6098434b533..43485866749a 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -41,7 +41,26 @@ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent) * __ptrace_unlink - unlink ptracee and restore its execution state * @child: ptracee to be unlinked * - * Remove @child from the ptrace list, move it back to the original parent. + * 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) @@ -55,25 +74,25 @@ void __ptrace_unlink(struct task_struct *child) list_del_init(&child->ptrace_entry); spin_lock(&child->sighand->siglock); - if (task_is_traced(child)) { - /* - * If group stop is completed or in progress, it should - * participate in the group stop. Set GROUP_STOP_PENDING - * before kicking it. - * - * This involves 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. - */ - if (child->signal->flags & SIGNAL_STOP_STOPPED || - child->signal->group_stop_count) - child->group_stop |= GROUP_STOP_PENDING; - signal_wake_up(child, 1); - } + + /* + * 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); } |